If i`am not mistaken Don uses the NMP header.You are using the Hatori flex header#HAT796.
I`am using a ES carbon fiber pipe with the Hatori#796 flex header.I have my pipe and header mounted with the Dave Brown hush clamp.
One at the end of the pipe and the other at the end of the header,were the pipe meets the header.I have 104 flights on my FOCUS 2 with the same header and it`s still going strong.
You have to have a header mount on your header,specially the flex headers otherwise the headers won`t last 10 flights each,believe me i broke about 4 Hatori flex headers in 1 month.In my other planes.
I modified the hush clamp so that i could use an aluminum hose clamp to tighten the header to the mount,it`s not the lightest way around but it works perfectly and to catch the pipe i use high temperature hose.With two clamps one for the pipe and one to tighten the header to the hush clamp.
You`ll have to make an additional wooden brace with a blind nut to rest the hush clamp where the pipe meets the header.Just the same like you did for the Pipe.
I hope this helps.