MADDMOE What size rear tire are you running? I have air ride and a 315/25/22. Depending on the pressure/height setting you run on the rear your rear tire can actually touch the horizontal plastic on the back of the Slingshot. Specifically the oval protrusion where the shock body goes through the rear plastic. So the location of the center mounted Welter pipes would be a real concern. It looks like the repositioning of the pipes you did should alleviate the concern.
......I just did 2 air ride installs, one on a 2016 and the other a 2019 and when both were dropped , there was no way a WP dual rear with that center pipe running directly behind the rear tire would fit, no way.....so i did what i had to do to keep my WPs dual rear because i love the sound and now i'm prepped for the air ride which will be my xmas present......oh and i'm running the 305 on the rear