PSRUs are a necessary evil for most conversions and frought with issues. we went through 3 designs and even had inflight failure with a prototype on our c172...I don't recommend the experience. problem is, it takes a lot of resources to develop and build one, way beyond that of most builders. so. ideally find a produced unit with long history and try to modify it to your engine.
I think you will find, however, you have to test it on your specific engine application and prop. the small things, like vibrations, are a factor of cumulative effects...for example, a wood prop vs aluminum prop .... alum will likely produce and amplify vibration more and become a factor OR be further amplified due to engine mount design, ect... problem is, few companies want to sell a gear box even for exp or have one utilitarian enough to fit different configurations....I only know a few. We had to develop our own after testing others.
we had dozens of inquiries for wanting to buy our design but because we only tested it in our configuration we were not sure how it would do on others and decided not to.
The other issue was FAA... even though our test plane was in EXP, we were told it still required to be treated as certified per part 47 and those doing mods had to be A&Ps. we didn't want to start over with another airframe ...but that's a long story. I recently updated earlier article on our FAA woes on air facts journal of you care to know more or need help falling asleep...link below.
Unfortunately, it became clear that FAA leadership had no interest in supporting such a solution—whether as an experimental conversion for certified airframes or via a STC (a certification that would allow owners to replace their original engine with ours on certified aircraft)—regardless of the...
airfactsjournal.com
point was that trying to build your own party would be expensive and difficult even with engineering background... I'd contact the few manufacturers out there and ask how it may be modified for your aircraft and what help they can give with testing. may the force b with u, if u do try building from scratch ...that's the beauty of EXP