Highlights of my "custom" Sargent "seat" included stitching that looked as if it had been done by a 9 year old and a seat cover that, in some places, was suspended a good 1/2" above the underlying foam. And yes, I contacted them about it...not that it did me any good at all.
The seat on my TBS, which I am very happy with, was made by Sprint Manufacturing (http://www.triumphparts.gbr.cc/
). You send them a seat pan, they fit their foam and cover and send it back. They do make one for the Street Triple, but I didn't want to give up my stock seat, so I bought the Corbin instead.