Take the allen heads to a machine shop. Get a HEX nutt made to the threads.Get lock tab, Lock tite the Hex bolt. put the lock tab on put the hex bolt through lock tab it and bam....Thing is'nt going to come out. They use it on cars too. I do believe.
So what keeps the tabs/clips from spinning? Are they roughed up on the bottom so they bite into the case? If that's the case wouldn't that flatten out some of the metal surfaces like under the clutch basket?
Here is a company making a setup that just may work.I am going to pursue having them make a kit.What do you think?Will having these on all bolts prevent the problem?trannyplate fasteners
These fasteners work by having something to lock against to prevent them from backing out. I dont know what you would plact the tabs against since the area we are talking about is pretty wide open.
Safety wire seems to be the best idea proposed so far.