Most of the issues listed about rotaries sound like things people hear from people who heard from people who....
I think that if you have a good data sample, you'll see that rotaries have no more issues with reduction drives than any of the other alternative engines. Ex: the old Ross drives (when built by senior Ross) seemed to work fine except for the fact that Ross failed to include an input shaft thrust bearing, to handle the thrust back into the engine shaft due to the helical cut gears in the planetary. The RWS follow-on does fine. Ex: the rotary is a 2-per-rev engine, like a 4 cyl 4 stroke. But, while a 4c/4s engine has a literal torque reversal on every rev, the rotary's power stroke lasts for significantly longer than 180 degrees, so the torque never reverses on a 2 rotor rotary. The overlapping torque curves look more like a 6 or 8 cyl engine.
It's worth remembering that one example does not (necessarily) define a problem. The old original Powersport shredded a coupling shaft on a dyno, but apparently, no one had checked on resonance issues with a 2 per rev engine running on a dyno that was set up for 4 per rev (8cyl) engines. Tracy Crook (RWS) proved conclusively that 'loose' systems (resonant point below min excitation frequency of the engine) can survive just as well as 'tight' (resonant point above highest freq of engine). P.S. also apparently shredded some drives by using heavy metal props. Well, if you don't design for high mass moment of inertia, you're probably going to shred some stuff. An additional data point on RWS drives that's not well known 'in the wild': Tracy's been running his Renesis powered RV-4 for several years, with no 'damper' (for lack of a better term) at all. There is enough lash in the gear set to keep resonance outside the critical range. He does specify no metal (high MMI) props, if the drive is operated without the 'damper' mechanism. Ex: shattered flex plates are very common, in most automotive engines regardless of make/model/type. I've got a 13B flex plate that's cracked; never been flown. And if you prowl the salvage yards, you'll see them on just about any auto trans car if you look around a bit. Ex: lash increasing over time is something you monitor, but it's something that happens in any gear set, including (and more critically) a 'zero lash' gear set. It is not, however, a significant issue in the planetary drives I'm familiar with, as long as proper use/maintenance is maintained.
Mark,
I hope you do enter the rotary market. But if you do, can you make sure the drive turns 'the right way'? Right hand rotation (tractor install, viewed from the cockpit) just makes more sense. It's easier to get a properly carved prop, and opens up the possibility of retaining a stock motor mount. I do like your drive ratio. 2.5 gets prop rpm in the 'normal' range, again making it easier to get a properly carved prop. It's really impressive how often the prop makers get it wrong, when dia & rpm get outside the 'normal' range for engines in this HP range (150-250 HP).
Charlie