I use an old large margarine tube under the bolt in the tank. It holds about 1/4 of the tank so I drain until it's near the top and then put the bolt back while I tip it out the tub. Not perfect but it works well
Early cars do not have a drain plug on the oil tank so I too have now invested in a vacuum oil extractor. It's a Sealey TP69 which has a 6.5 Ltr capacity which should be just about right. Around £45 on eBay.
Ok, dry sump, I understand that..still unsure why MMC doesn't fit a drain plug that's easy to get at, but it is what it is.
My dealer is 2+ hrs away, so any DIY maintenance is a plus. What's the service interval? I'm afraid to ask about the oil filter...there IS one of those, yes, and is it accessible?
Service intervals are yearly or 3000 miles after first service at 3 months 1000 miles. Some things are out of phase, if extensive idling/ low speed running or dusty conditions every 5000miles inspect brake system & replace spark plugs & 15000 replace fuel filter. The book does not say intervals for those in normal conditions. The oil filter is low on L/H side of engine inboard of the suspension mount. There is not much clearance but no plastic shrouds to remove, no doubt Q8 or JVS could add further. Oil filters cost £9.37 & fuel filters £78.10 plus tax. My dealer books 4.5 hrs for service.
If you're doing your own servicing, genuine fuel filters can be bought on eBay for under £40 inc P&P. And genuine Harley 'black' oil filters are around £5 inc P&P.