fabbed up my exhaust with a home made portmatched flange made from flat stock allowed me to run a extra large header pipe.
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If you don't mind I would like to make a suggestion?
Where that exhaust comes across the front down tube . We did one with that pipe and used strap steel and PDM membrane type rubber. Basically it is denser than inner tubing for a Bike tire. Old thorn proof tubing might be better?
Depends how well you craft the clamp
Get muffler clamps for small exhaust at Napa over here when we did it. Take your strap steel and carefully bend it to match the down tube. Mock the whole clamp in then tack weld it. Tack it to the pipe. Tack the pipe off. Last stitch weld it letting it cool down a bit as you go, so not to worp any thing or blow through your metel. Done!
The strap steel will be what meets up with your frame. Instead of those nasty gash marks a bare clamp would make to it self and to the pipe. You're resilient rubber will protect your frame and hold stuff permanent like.
Note this will great if the motor is solid too. Of course.
This will help tunning fork through the bike type vibrations. Last can add uni-body structure helping the engine etc to sit still where ya want it! uni-bodystructure always does add strength to any creation IMHO. It can also add weight lol. My favorite way to think of when I think of building structures. Wood work etc.