In full length tuned pipse - I have tried a numberof types -all very long and very large .
There are US made - Mac's, and AUS Bolly and Czech (?) and KS from Germany.
BUT-- so far - the KS -setup right -is the best all around for gas pattern stuff.
Count on these things occupying lots of length and if you can PLEASE- set them up in tunnels exposed to air -preferrably along a goodly section of the belly of the plane.
Tuned pipes need to operate at fairly stable temps and high rises in heat raise bloody hell with their performance.
We have run the 50 3W but that is the only 3W on tuned stuff No reason the 75 won't work well but I would use a tuned pipe at least as large as the 80 KS series. On the 80 ZDZ and the 160 ZDZ this pipe really Works!
keep headers of large dia's and if at all possible do all preliminary setup for prop and pipe length on a bench.
The common mistake is overpropping (really dumb) and header too short and top end needles too lean.
Pipes make more power because --they burn more fuel----