Still plodding along. when I first attempted to mount the final drives on a model I discovered the shortcoming of my shortcut for mounting the
sprocket to the drive shafts. It was impossible to line up the 20 small( 1-72 ) screws/bolts to the sprocket shell. I had fabricated a steel flange which I pinned
to the output shaft and the holes for the 20 mounting screws were clearance holes which allowed the screws to wiggle and waggle anyway they wanted. Bad idea.
So I decided to make the parts I should have in the first place but hadn't as I knew they'd be hell a'devil to make. I had to thread 200 1-72 sized holes through 1/4" thick
aluminum so the screws would remain positioned correctly. Well I threaded those 200 holes and managed to not break a tap in the process. The initial test is good.....

Jerry