Zip,
Mac's is the place to get a full pipe.
But let me make a suggestion. Take a look at the muffler installed in the Patriot XL thread. That same jett-stream muffler is available for the G75, and will give you very close to the same performance you will get with a full pipe. Just none of the hassles. Ends up costing about the same when you are done.
Being a pattern guy from back in the 80's, yeah.... it probably needs the big pipe for the 'authentic look'....
But just suggested as an alternative.
Any questions, drop me a PM
Bob