Answer to Diablo:
I'm using a Stihl filter. It has a cylindrical plastic housing with a fine mesh filter element. It has very low flow resistance, and is still heavy enough to stay at the low point. Remember this setup worked for over 30 flights.

I looked at the thread mentioned above by Bob. I removed the insulator and valve block. The fasteners attaching the insulator were not very tight, and there was some evidence of leakage between the insulator and valve block. I can't see where warping could be a problem, since the seals are very thick. I can see where the seals could have compressed over time, effectively loosening the fasteners. I put a light coat of red RTV on all seal surfaces, and reassembled everything. I did not have a chance to fly today. I still plan to get the carb kit.

Thanks
Cliff