We had a s300 machined to accept a standard 3" vband.
Makes fitment much easy.
No need for reducers or special exhaust flanges.
Standard 3" vband flange works perfect.
You can see in the pic that 3" tubing is still much larger then the wheel discharge port.

 

Thats a cute little guy! I bet two of them would be fun.

Maching the housing for a male vband is the way to go, makes it so much easier.

 

They have rated them at about 1100hp each for the billet s371 in twin applications...

 

Looks good