My Rascal 40 started life with a ASP .52 four stroke and it just did
not like to idle while mounted inverted. Upright, it would run just
fine. I installed a MPI on-board glow driver and it fixed the idle
problem, but I now had bad radio glitches in-flight. Not wanting
to risk the plane any further, I replaced the ASP with a OS .52
four stroke and it was just like night and day. It had great idle and pulled the plane better than the ASP. And without the glow
driver. You should be fine with the OS as long as it is broken in
right and adjusted well.