At times I get the feeling that I have taken on far more than I can chew given that I'm neither an aerospace or mechanical engineer...That's quite a project. As a professionally engineered unit, there should be good information on the inertial characteristics of the fan assembly and any gearing, which may be of use to you.
Who is that? Very few people have even heard of them so anyone who knows of them on this site would be a useful contact.They are exotic looking airplanes. One of our frequent posters on this site still holds them up as good performers.
At the moment I've done a lot of guestimates of what the change will mean, for the rotary engine I'm planning on using the aftermarket alloy end and centre plates which will bring the engine weight down very similar to the Allison's 114 kg, but then I have to add in radiators, coolant etc. I will get back some weight with the removal of the ejection seats and replacing them with carbon fibre motorsport seats.I'm sure you've looked into the weight and balance issues, I would think they are significant. A 650HP Wankel will be lighter than a piston alternative, but heavier than a turbine. You'll get some of that weight back due to the lower fuel requirements, hopefully it will be in the right place.
I'm certainly hoping to succeed with the Wankel to fan connection as I haven't really considered any alternatives. The performance of the planes that have the Allison + fan & duct is very satisfactory so hopefully I can make it work as it will be a sweet plane to fly if I do.You'd probably prefer to maintain the looks of the plane as is. However, if the engineering challenges of mating a Wankel to the existing driveline become too much, you might at least consider going with an open pusher prop with a PSRU, if you can make it work from a packaging perspective. The drag from that shroud is likely considerable, I'd imagine service parts for the proprietary fan unit will not be easy to get, and a conventional PSRU and prop may provide increased cruise thrust in comparison.