Sure, it's been done. I can't remember the name of the guy who had
twin small SuperTrapps on his 6 at the National in ... Seattle?
Someone will help me out. You could use the "concealed" model
and tuck it away under the boot. Or you could weld just the
arrestors on the end of the exit pipes.
I have a ST on my GT6+:
and I quite like it. That sort of installation isn't quite right
for a TR6, but I'm sure you can up with something. I made some custom
brackets and put it all together with flex hose until I was happy
with it, then took it to a muffler shop to make up out of real tubing.