Wouldn't you be better off making up some suitable flanges and using spings to slip-fit the pipes to the flanges, Wayne?

I've always assumed that thin walled race style chambers use this kind of set up in part to avoid having a 'solid' mounting at the pipe header that could crack due to vibration. As it's probably not much more hassle to fabricate some suitable flanges than it would be to 'cut and shut' the pipes (and potentially ruin 2 sets of pipes in the process) I'd definitely favour the flange option as that would mean that the JHA's would be unmolested and therfore eminently more 'sellable' if you find you don't want them or want to try different pipes.

Just my bit, really...

Rgds

Wb