The ST90 converted to gas that I have on my Tiger 60 is running at 16:1 like my 51 with no bearings on the rod. Haven't had any problems at all and yes the power is down some from glow but not as much as I thought it would be. I did machine the head some to raise the C/R and I am running a Walbro carb but otherwise the basic engine is as delivered. CH makes a Hall Effect mount that doesn't require any machining of the case and it's very easy to set the timing. It spins a 14X6 9800 to 9900. On a real good day it'll get 10,000. (my 95AX on 10% turns the exact same prop 10,300) Never tried either with a 13X6 so I can't be of help there. As far as starting goes it starts pretty easy after the first start of the day. I usually use the electric starter for the first start and then hand prop it after it's warmed up. Average flying will use about 6oz in 12mins. The little Rimfire plugs last 30+ hours and run around 16 bucks depending on where you get them. Mine is running a genuine CH CDI box and 1000 mah pack which is good for longer than I care to fly in a day. (An hours flying will require about 300ma to bring it back to full charge)

While I haven't owned the BME90 I have been considering buying one so I can run the same fuel as my 26 and 50cc stuff at 40:1. Also, I understand the needle bearings bring the HP up some more making it even more powerful and for a sport flyer any more than mine makes is just icing on the cake, IMHO.