Service Ceiling for a C85 powered 415-C?

I've been curious for a long time. Since I'm a sport pilot, I'm not allowed above 10,000, except to avoid terrain... and there's nothing tall enough on the east coast to qualify.

I have flown to 9900 (C85 "stroker" with a McCauley 1A90 73/49.) At that point I was still climbing at 250-300 FPM - solo with slightly more than half fuel. It was an interesting flight since it was 97 degrees on the ground, and as I climbed it became more comfortable to close the windows and then to crack open the heater. On the way down, experiencing the return to 97 degree heat was a lot less fun.

Sweet, good memories, sounds like a great trip!

I was stopping in Cut Bank to visit friends. So, from Seattle we followed i-90 to Missoula, then angled towards Lincoln MT following MT200 and crossed the divide at Rogers Pass. Then headed North. We ran out of light and spent the night in the pilots lounge at Choteau (really nice pilot lounge with fresh fruit, drinks, and snacks and a loner car), then continued to Cut Bank the next morning. That was my favorite leg of the entire trip, flying over flat farm land with the rugged continental divide, Bob Marshall Wilderness, and Glacier Park, just a few miles off the wing tip.

Understood on the altitude and loadout. And with a DA of +2000 to boot that is good to know! Looks like we have the same prop. Looks like it was a gorgeous flight! Did you fly over Helena or down to I-90 then over?

I climbed to 9500 with a C85 with 48" pitch propeller flying over the Rockies enroute to Oshkosh. DA was around +2000 on a warm calm afternoon when I took off from Missoula heading East, loaded to 1400#. So that might be around 11000' on a standard day. IAS was down to 75 mph, so I wasn't going to get much more out of her. But it was enough to clear the continental divide by a couple thousand feet.

I'm hearing 13,000, Youtube saying 12,000, and others saying 11,000. Does anyone have actual numbers they've flown? If Old Man winter would be kind and give me a sunny day I plan on trying it in mine, meantime what are your experiences with max ceilings? This ties in to looking at long cross country flights with my wife come next spring/summer.