The biggest problem comes at overhaul time (which is a large factor of hours earlier on the RR engine compared to the 235) and that is if the crankshaft gets condemned. We used to operate an FRA 150 and the crank only got through that process with some very clever work by a top engine man. However, it was made plain it could not be used again at the next overhaul. While this was going on we tried tirelessly to find a replacement - worldwide - without any success. Of course, your Authority may allow the use of a newly made crank from one of the excellent machine shops in North America as is indeed the case in FAA land. The UK CAA would not countenance such a proposal. We had similar problems with the unique exhaust system and some other unique parts. We now have an A152 instead.