The L7 can be fitted with a PBU stage pipe without modification to pipe or frame, and the rear exhaust mount lines up perfectly

You do have to cut an oval hole in the bottom fairing to clear part of the header pipe though.
We ran PBU C/F Reeds/Block with a Walbro 16.5 Carby, but had to cut down a foam unifilter so it fitted (There is not as much room between the back of the crankcase and front of the rear tyre as on most other bikes)
Mark from Ozscoot said some time ago that he could probably get genuine L7 fairings, maybe check out Carter? Standard Carter/Pocketracer fairings will not fit. Tips with the fairings
...put a spacer tube on the front seat screw between the frame and fairing so you don't crack the fairing by overtightening/crushing it.
...Put a steel washer inside the lower fairing screws so the little peg does not wear into the fairing and a rubber one under the head of the screw
Standard windscreens do just fit, slightly different shape, but not noticable when fitted.
Alan