Yes, do not run a heavy hub on your dieselized Tower 40.
I also had a problem with the contrapiston of the RJL head coming apart. The O-ring groove was too close to the face and a circle of metal separated and really overcompressed the engine.
Gene Hemple made me a new contapiston with a thicker shelf and it has been doing fine. I've put in a few runs on a Magnum Pro 40. I tried to run muffler pressure, as I did with the Tower 40, and it did not work well. Took the muffler off and it ran fine. I flew it through two OTS patterns before the outside wing on my old #7 Easy blew off.
I ran the Tower 40 probably 1000 flights glow with the heavy hub and no problem. But I went through four crankshafts in a few hundred flights running diesel. Others have had no problem flying dieselized Tower 40's, so I think (hope) the heavy hub was the problem.