Max Gross Weight (1400 lbs) at 10,500 MSL

In my C90 powered M10 with cruise prop, I have been over 10,000 feet several times. The first was to get my ADS-B rebate. I climbed to 10,500 and stayed there for an hour. A second time I climbed to over 11,000 to avoid little pop up thunderstorms. It was smooth and cool up there and I just avoided the tops of the storms. I also was able to lean the motor out and cut my fuel flow by 30%. I was solo both times and it took a while to get up there and also took a long time to get down.

Interestingly enough, last month I found myself at 11,000 feet in Nevada, with a density altitude of 15,400 - Not due to my climbing that high, but due to significant thermal activity. Temperature was over 100 f at ground level and got down to around 78 at that altitude. We did not stay that high long... LOL!
Forney F-1 with C-90 and climb prop.

Your gross weight is 1260 unless you have the 1320 STC. The C85's with the O-200 crank on a cool day would have a good shot at it. Even with an O-200 or C-90 and climb prop you need patience to get to 10,000. You will probably do it once.

Should my 1946 Ercoupe 415C be capable of performing at max gross weight at 10,500 MSL?