Link pipe size

I chopping up the original exhaust with my trusty axe to get the link pipe .

The outer diameter of that pipe is approx. 67 mm .Inside that pipe is another pipe( which the gases flow )with a diam of approx 50 mm.
I have noticed on other link pipes it starts off large, gets smaller ,then gets larger to join the can .
Is 67 mm too large ,and optimum performance is actually better with a more restrictive pipe ?

The link pipe in the pic above in place.

There is a fair bit of science involved in designing an exhaust system plus the added visual requirement from our style of bike.
Twin walled pipes are used to limit discoloration of the outer SS but I’m sure you already knew that
Pipe size shape and length is determined by the intended operating range of the engine and where the manufacturer wants the sweet spot to be considering all other factors (including legal limitations) Here is some info I quickly googled. http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm
I know its from a car site but the principals are the same.

Forgot about the colour thing .The link pipe i made had a large diam. i worried it might have been too big . There was so much metal in the
original link pipe ,and it wasnt just one pipe inside another and cut off even both ends .

gus wrote:Forgot about the colour thing .The link pipe i made had a large diam. i worried it might have been too big . There was so much metal in the
original link pipe ,and it wasnt just one pipe inside another and cut off even both ends .

The cat is the restrictor in our systems Gus. I would think that once the gasses pass through the headers and the cat we probably could have any size pipe we like (bigger than original) without much detrimental effect on performance.