Here's a refresh. first the front fasteners. Front pair through the chassis, second pair through the floorboards.
Runners are straight onto the carpet.

And the rears which are inside the U shaped runners and need a thinwall socket/tube spanner or an open ender, end on.

This is what holds the seat in place:
The rear bolts are longer as they pass through the thick part of the chassis which also has the spring front mounts.

Lift the seat out and this is what you get:

The underside of the seat. I don't see any difference to the Roadster to be honest. Note the protruding nuts. They press into the floorboards if you don't have spacers.

You can see how far it protrodes here:

My new runners, with hole for those protruding nuts.

It's a match......

Test Fit:

Nearly there:(note stainless chassis cover!)

And this is the difference it makes!!!
For a shorty like me, this is much better, but still have to do it all again tomorrow for the drivers side.
The front 4 bolts need to be 2.5". The rear pair need to be 3.5", so I've had to order some because I've only got one 3.5" bolt in stock. Grrrrrr!

Update from 2017 - before I sold Bumble, I removed these spacers which were just a bit too deep, and replaced them with some which were about half the thickness.