"If the pipe or coupler gets a pinhole leak in it you'd never doubt that!"
I gotta ask, not having had any problems with either (PA .51 or OS .46VF AAC) engine I've flown on a CF pipe setup. What happens if you do get a pinhole leak in the pipe or coupler? Can I assume that a leak at the header/engine joint would do the same?
When I asked a guy (whose initials are "PW") about his testing of a "big block" in his plane what that engine was, he said it was a RO-Jett .76. He also said that he really liked the way the engine produced "power" but it HAD to be "loaded down", with a large prop. And that his airplane didn't like a 14" prop. Some of this may have had to do with what props were on hand, I'd guess.
I think specifically, the large diameter prop killed the VERY HARD corner for which he is well known. Quite possibly causes difficulties in the hourglass also? This suggests that some 4 blade Brian Eather props would be desirable. Brian Eather will tell you that he wasn't satisfied with the .76 on a pipe, so ran it on a muffler.
Matt, those Magnum XLS .52 restrictors are still on my mind...I tore the shop all up and it's going back together now. Insulation, electrical, moving heavy stuff, etc....ugh!
Steve