the bottom end gives a high idle, if you play with it you can get it lower, then it'll cut in the air, but what the heck do you want to cut it in the air for? fly it dry you jessy, it's what i have to do on my GRRT with no throttle
the running in is spot on, both my Wests have flown right fro the start, only the 50 got a quick ground check first to make sure it wouldn't cut.
if your in the air the engine is at it's normal running temp, so the piston liner relationship is as it will be. if you run on the ground and hot, or rich and cool the piston and liner will have a different relationship, so when you to final settings it'll all be the wrong shape and... worn out.
now I'm away from old gummy castor and old style engines this is what i do with every engine, tho the other makes get a few richish flights before leaning out.