RE: moki reverse crank
Just my question - do you really need counter-rotating props????
Neither do I know the plane you are going to build nor the engines, but my experience from building many twins and multis is that I never needed counter rotating props. Sure, it looks great and may have some aerodynamic benefits, but for my purposes (e.g. on planes like the A.W. Whitley or the Turbo Panda, not fast planes but model twins that can be flown quite aggressively), I wasn't able to feel (in flight) a difference between counter-rotating and not-counter-rotating props....
I think the greatest "benefit" of using normal engines is, besides the lower price of the whole thing, the one that there is a vast variety of different propellers to fit your needs best. There is only a small sortiment of left-running props!
best regards
Chris