ORIGINAL: Antique
Our T6s weigh at least 26 lbs...
I flew a Ziroli T-6 for years and it weighed well over 30 pounds. It flew with a G-62 for most of its life then later on it had (still has) a FPE 4.2. I no longer remember the prop size used on the G-62 (CRS disease ya know) but the 4.2 uses a 24-10 with excellent overall performance. The performance differences between the engines was minimal. It is no racer by any means but performance is good throughout the whole flight envelope.
Back to the OP's request, I'd use the prop I have on hand for starters then adjust the size from there as a compromise to keep the engine and airframe happy.