Repost from Extreme Speed forum -

I've got a couple of pipe issues. I had the solutions from the former forum but now can't find them. I'm hoping that some of you can help me out with dimensions (Mr. Auger...).
On a Shrike .40 I've got an older O.S. 46 VFR? Rear exhaust with a MACS kick up header and pipe. What length should I be going for to start tuning? I'm running an AP 9x9 but could run an 8X8 which I think is the optimal prop.
On a Shrike .10 I've got an MVVS .21 with the silencer muffler bolted directly to the engine (no header length). What prop and pipe should I be using? Before I go and modify the fuse for the silencer I'd like to know if a non-silencing pipe is advantagious. I also have an MVVS .26 Combat Special that I could put oon instead but need to come up with a pipe for it.
On a Direct Connection F-20 (F-5) .40 size, I've got a Jett .50 side exaust with the Jett sport muffler. Would it be worthwhile to put it on a pipe and what prop?
Summer's on it's way and we'll start airshow racing soon, I just want to go fast. Are there pre-set headers and pipes availible?

Thanks for your help,
Chris