lhoffman
Another option would be to get the neck of your "Tranny" re-angled. Ernie Sola did this to my 10M and its really a great modification, which, along with lowering the strap hook and replacing the thumb hook with a modern (i.e. Selmer styled) thumbhook (and in the case of my horn several other things), substantially improve the ergonomics of the horn. Frankly, I don't know how he did it, other than it involved removing the tenon or tenon receiver from the horn and re-attaching it an the desired angle. Since the change is pretty small, the overall length of the horn is not really affected. Check with your repairman about this one. If he/she doesn't do this sort of work, I'd suggest contacting someone like Curt or Randy Jones.
You may find that the horn won't tune with a modern neck, so be careful. I had a Gloger (from Curt, who was great to deal with) for another 10M which worked well, but the curve was the same as that of the stock neck.