Al,
Your approach has worked for some. The stick in the bypass has been used for years to cure the "Fox Burp" particularly on profiles. You may have made it to wide which blocked off to much. Also, could just be that you loaded them motor more than what the conditions would let it cool properly, this is usually over prop. An open exhaust Fox35 can run a 10x6 prop when running at least 25% (50/50) oil. If you run a muffler you need to reduce the prop diameter about 1/2" (sometimes more, depending on the muffler type). In the earlier post you mentioned you were running GMA 10/22. With that low % oil it will do just what you say. Read Randy's post at the top of the forum about fuel for steel/iron plain bearing engines. The Fox uses oil to do two things, one is remove heat and second to increase the compression. I run the stock head, 7%N, 27% oil on a BYO 10x6 cut to 9 5/8" with a tube muffler, this works well in my 34oz El Diablo.
Best, DennisT