I run an OS 70 FS inverted in a GLOBAL AVENGER plane and have no trouble! I'm running an OS 4 stroke plug in it. I do give it a little extra time on the ground for warm up. and I run her up good before I go out to taxi. (YOU DO HAVE TO DO THE ENGINE ADJUSTING WHILE IT IS IN THE INVERTED POSITION)
I have a friend that flies "war birds" and all of his 2 and 4 strokes are running inverted. He does not have a problem either.

But the glow igniter is still a great idea! I bought one on E-BAY to give a try.
RON in NEVADA