Hi All, I switched from a 600 cc Dominator to a 1972 750 Commando engine in my Featherbed slimlime chassis a few months ago. I got plenty of advices from this forum and from other guys who had done it. I used 8 mm 4G / 2017 alloy (I don't know to which grade it corresponds in US - UK standards) to build the gearbox and engine plates. I designed them so that the engine is "as low and as forward" as possible. I was a bit concerned with the possibility of re-using standard Commando exhaust pipes and being able to take off the cylinder head whilst keeping the engine in the frame, but all went well. The most complex issue was with adapting the central and side stands to the new plates. Lots of drawings / measurements / cutting & welding but no unsolvable problem. Re: the solution to keep the vibrations within acceptable range (ie keeping only the good vibes!), I started with the most attractive one (Featherlastic) but the guys who did that in the US (Mike Harcourt, Randy Ullery, Ron Fraturelli) could not help me and I felt not able to make it properly on my own and starting from scratch. Then I considered having all the moving parts carefully dynamically re-balanced but I opted eventually for Jim Schmidt's longer rods / lighter pistons / standard camshaft package and I am very satisfied with the result. From my experience, vibrations are lower than when I had a 500 cc / single carb engine. The engine power curve is very pleasant and fits exactly my type of riding. Furthermore, Jim is very reactive and very helpful. With about 4000 miles of experience with that engine now, no broken plate neither loose nut nor any damage caused by vibrations. L.