The SuperTigre Silent muffler:

SUPG1559 12523530 SILENT MUFFLER S-3000

is adjustable, and should get the clearance you need. Unfortunatelyl, these are out of stock and won't be available until we get G3250's later this year. You may be able to locate one through the 'swap shop' areas, here on RCU.

We're not familiar enough with the Jtec mufflers to give you an answer. Sometimes, though, you can have a machinist friend make you an extension that will do the job.