(EDIT: For GM automatics)
I make a lot of tools.
I also like drawing up plans, and writing instructions.
While this tool is pretty simple, a set of instructions can't hurt.
Free, because I can't be bothered to hide them and try and make money off them. Spreading the love.
Transmission Stand Plans
My only thought is to maybe put a threaded rod from the top center hole of the bell housing to the top center of the tool. This would allow you to rotate the transmission to work on it.
I'm not picturing what you're saying.
The stand with the trans in it, has a single threaded hole with a long bolt that is stopped against the trans, theoretically making them rotate/move as one. The trans and "u" rotate in the engine stand easy. Vertical, horizontal, perfectly.
I did find that a single bolt just wasn't stable enough, so I now use two bolts on either side of the stand and it's much better. The whole freaky-deaky thing totally rotates easy.
Stupid question... but are there holes on the side of the trans that the bolts go into? Can't say I've ever noticed that before.
At least on gm automatics there are divots in the casting for this purpose