My engines are put in horizontal. If I had it to do again, I'd put them about 30 degrees above horizontal. You have to use a real short glow igniter to get to the one engine.
I haven't run any inverted engines for years. Just had too much trouble with them putting out the fire at idle speeds. On board ignition I guess would solve that.
The retracts are air operated. That's all I've ever used. Apparently I've been lucky. Talked to lots of people that has had problems with them.
I covered mine with worldtex and Champion spray camo paint. Worked well.
Randy