Ian Savage's A comet centre stand was the inspiration for me to fit a centre stand to my A twin. I also had advice from Dave Hills. It transformed the use of the bike, the rear stand is even more of a strain than the C stand.
Bob Stafford told me he could only have one go at the rear stand and if not successful had to have help.
Back to A twin centre stand, I made mine shorter than Ian's, when down both front and rear wheels are still on the ground, this makes it extremely easy to use, the stand has a extension so you can use your foot to lower the stand. When I want the rear wheel off the ground I use "packing pieces"under the legs while tilting the bike from side to side. It did take a long time to fathom out what length to use on the legs and what angle to use, and what shape for the pads on the end of the legs. Changes to the bike are minimal: two modified gearbox nuts (using the existing nuts), these for the stand pivots, and one 1/4 inch hole drilled in offside plate, for a stop when stand is up. I found a coded welder to weld up the stand, no backstreet sheet metal welder is to be trusted with a safety critical job. Some time ago I took photos of the stand, if I can find them I could put them up. Best of luck with the stand for the A Comet it will improve the use of the bike.