Resurrecting the thread...
I wound up getting the Delkevic full 17" oval system and have had it on for about 4 weeks now. The factory cans have an indent to allow for clearance of the axle but the Delkevics do not. It looks like I will have to loosen the clamp at the front of the can and the mounting clamp on the footrest hanger to rotate the can out of the way if the rear tire has to come off. Since this is a nice stainless system, the clamps shouldn't rust up tight. Time will tell.
The new system sounds a bit different than the factory pipes. No surprise there. It is definitely a bit more of a throaty, aggressive sound but not too bad. At highway speeds it's not much louder that factory. The ST seems more responsive but without dyno readings, any improvement in performance is subjective. Calibrated seat-of-the-pants evaluation is a thumbs up! Delkevic says you don't have to re-tune the motor or re-jet but I had the carbs re-synced anyway. I have not done that since I've had the bike. She runs much better and I am happy with the change. One odd thing I did notice is that I can feel more of the motor's "presence" in the foot pegs in the 2000-2300 RPM range. It's not engine vibrations but I think it's more like sympathetic firing impulses coming through that can be felt through the foot pegs. At highway speeds, she's as smooth as she ever was. I would recommend these pipes to anybody.