Exhaust for KN 93

I am building a Board Track themed bike around a KN 93, my questions are concerning the exhaust at this point. I would like to run the straight pipe design seen on some of the old BT Racers, however I am concerned about getting a good exhaust seal without using goo. I will be designing the exhaust in SolidWorks, and can get some pretty fine tolerances if I need to have something CNC machined. Any suggestions would be useful considering how to mount the exhaust header pipe, can I press fit as there does not seem to be any way to flange bolt without modification of the heads, required minimum exhaust tube length.

Thank you

I use a pipe expander to make the head pipe a good tight fit in the port, and then weld a tab on the pipe and drill a small hole in a fin and add a spring.

Here's a shot of Lee Wickstrom's Knucklehead drag bike with springs helping to hold the pipes on.

Wow, thanks for the tip Do you use some type of gasket

I just go with as tight a fit as I can get to fit into the port, but I have been told that if you paint some molasses on the part of the pipe that goes into the port it'll bake on and seal the pipe, I've never tried though.