I've got a half tuned MVVS 40 on mine, i lost the bottom covering on the first flight with the pipe untunned and now use Solartex, top covering is still film, but i have sealer and tape on every joint and wrapped around the L.E
i have no problem getting throwers for me, they love to see it blast off.
As for engines, Webra should soon be 'producing' a 3bhp 50 engine, we get these in the UK next week hopefully and the price so far is £150 for engine, pipe and manifold.
A DD with a fully tunned MVVS 40 ( mine with old owner ) reached the engines/prop max speed, it just couldnt go faster, a very clean airframe this.
For some reason he got bored of it, sold it to someone else, they never did anything with it and gave! it to me WITH ENGINE! when i brought his shrike with engine. very happy me