Well each to their own, but again the addition of the stay above the conical washers will not effect the seating angle selected to align with the pillar and to place an un-engineered and irregular shape beneath them will negate the accuracy required as well as the stability of the set angle, potentially exerting a force which could also lead to a potential failure of the washer set. Just remember, MMC didn't design the stays and in fact were not fitting them as standard when clearly they were needed to stabilise the front cross head for years previously and indeed didn't fit them right up until the end of production. yes ,exceptions where outside performance improved limited edition vehicles like the ARP etc. were specified, and were supplied fitted as standard.
But clearly not the norm!

To quote MMC is a little too brave for me as they are well known for having their design or elements of it challenged and changed by aftermarket engineers/specialists. look again at how the washer set sits when on top of the stay at tell me hand on heart that that's a cracking design!

With regard to Cain's experience of an exploding washer it can only be down to an incorrectly tempered item and regardless of lubrication it would have shattered when stressed every time. Wolf performance are hugely experienced and knowledgeable and Cain doesn't get it wrong so I hear your reasoning in regard to the conical washer set but as an engineer myself I still would not fit the washers above the irregular and somewhat hit and miss nature of the stay with or without the welded reinforcement washer.

Perhaps others who have had the stays fitted for them might have an opinion to share here. Perhaps they fitted them themselves and were advised on the location when doing so. Would be nice to hear from them of their opinion here too!

There is one little tip I feel I should share for those thinking of fitting their own stays regardless of where they choose to fit the conical washer set if they have a post 2011 car.
Most get into trouble with what is a very simple DIY job by losing the location of the pillar at the top shock absorber mounting plate when removing the oiler bolt. So here's a very brief step guide to the procedure:

Loosen wheel nuts/spinner's of front wheels on the ground.

Jack the front of the vehicle having chocked the rear wheels .use the centre of the lower cross head tube(axel tube) as your jacking point.

Place support stands each side of the centre cross braced middle section of the cross head on the axel tube on the outboard side of the centre square section. Not on the joint reinforcement areas.

Loosen the oiler bolt ( if you have the oiler system fitted remove oil pipe first) You will need A/F spanners.

Now here's the vital bit..... place a jack under the lower pillar nut and carefully jack until you are holding the pillar against the top mount. you do not need to exert a force that will lift the car from the axel stand. Rather you are just maintaining its location in the top mount!

You can now remove the oiler bolt and there will be no spring deflection to allow the misalignment of the pillar.

Fit the top mount end of the stay to your oiler bolt; appertaining to your vehicle type for sequence.

At this point tighten the oiler bolt up snugly especially if the stay is fitted with the welded re-enforcing washer. then loosen enough to swing the stay into position on the chassis. I have always found that the angles of the flattened sections will need a slight adjustment to fit flat against the chassis and also achieve a satisfactory marking template and no induced stresses through a misaligned tightening.
Before marking, consider it's position on the chassis. It is desirable that you fit it as closely as possible to the vertical element of the chassis rail and if your flat fitting area is small you might consider relieving the square edge of the flattened stay which abuts against the chassis wall to get a closer fit. I would recommend this in all cases even though its not suggested by suppliers to retain maximum chassis integrity.

Use the stay to mark the location of the hole to be drilled in the chassis. If you have a problem drill wise re. access to drill from above, take a small piece of card, push it against the vertical chassis and fold it under the bottom edge. now using the stay, mark the hole onto the card. Now remove the card and push a small screwdriver through the card in the Centre of the hole, through both sides when folded. Return the card to the chassis using the small screwdriver to align the card correctly to the top side by placing the screwdriver point in the centre of the originally marked chassis and slide the card down. fold it underneath and you can now transfer the top centre mark to below. You will need to centre punch a start mark for the drill to prevent it walking and drilling an incorrect position! Now you can drill from underneath!

An 8mm hole size is required but start with a 5mm and step up to 8/8.5mm. Some chassis' can be very hard and a good drill bit is necessary. Some Instruction I have seen say's to drill a 12mm hole but this I feel is to allow for misalignment errors. I'd suggest only do this if you have made that error and step up slowly until a fit is achieved keeping the hole as small as possible.

Now tighten everything up and do the same to the other side.

The stays originally used to be supplied with bolts that were able to shear in the event of an accident to limit damage to chassis etc. The last set I fitted were supplied with 8.8 high tensile steel variants designed not to shear or provide a weak link. I am experimenting with 5/16" brass bolts at the moment to see if they will suffice in normal use..... so far so good on regular inspection! I'll report after a year or so as this is experimental at this time and I have made provision for the stay to remain in position in case of failure.

That for me is it I think, I feel I have exhausted my input on this matter. I hope I have helped those who might wish to fit their own cross head top support stays, it really is a simple job using basic garage tools and might save you some money towards you next upgrade or accessory.