A The Dyn'Aero MCR01 or a Diamond DA20 are both good marks to hit. To get the same specs for $30k per member would be a reasonable goal. With good design and scrounging it can be done. Think about coordinating with people that currently have molds for wing skins, canopies, cowls, etc... and start working deals for a set of parts and design and build the rest. Get out of the box on how to make parts and molds for cheap for a few or a dozen sets of parts and solve those problems and then start filling in the blanks. All doable.
I like the MCR01, maybe that could be the target but balance it out a bit with aspects of the DA20, and Autoreply pointed out the Europa, also a nice plane. So we could use as models the MCR01, DA20, Europa, and also at the end of the spectrum the CTSW. The MCR01 is impressive in that it cruises at 170mph (the earlier figure was incorrect) on 80HP. But it is probably cramped in the cockpit, and maybe could be tones down a bit, increase wing area a little, but we could increase the HP to compensate to 100hp. That is what I feel is a good target. Of the 4 planes listed 100hp is about the mean. So, I feel a carbon fiber airframe with 100hp engine is a good target and borrowing heavily from the MCR01 design.About 850cc dry sump twin water cooled with a turbo and EFI would be a nice little engine. About 100HP at FL10 would be nice. A belt drive PSRU or a Rotax B box would work.
How much do you think that would set you back and how much do you think it would weigh?
As for the engine, I was reading through the auto conversion forum and came across a thread that talked about turbocharging an engine at a lower rpm. Think about this for a second. Take the Hyundai 1.6 Ltr Gamma engine just as an example of what's out there. 138HP at 6300rpm and weighing about 210 LBS, a little heavier than a rotax 100hp but not much. If we derate it to 100hp what rpm would that be? I could not find a dyno on the engine so...a guess might be at 5000rpm (or maybe 4500). What rpm are we shooting for? The Aerovee is 3400rpm, the guy who had the very successful Long EZ conversion with an LS1 engine had in direct drive at 3500rpm. Catto props made a 3-blade prop for this engine that they still sell. Maybe 3500rpm would be a good target, it is not too low that we would have to over boost the engine. We would give up some prop efficiency but maybe make it up by increasing HP to 105.
So, we find an auto engine with good characteristics for boosting, match it with a good turbocharger, and boost it at 3500rpm to get to 105HP. This with an emphasis on avoiding detonation and torsional vibration. And this solution would avoid the complexity of a PSRU.