Hey Luke, yeah when you open the carb up you may need to enlarge the idle hole in the little copper tube in the SHA. Take a leedle large enough to fit into the hole (holes) in it and gently widen the opening slightly. Also make sure your idle screw is turned in - probably all the way.
I haven't been able to test mine much because I need an 11mm cone lock nut on the rear wheel before I can drive it.
I did the piston and cylinder porting mentioned above and on my one test it seemed quite a bit faster than the 25 stock. I only put a 54 jet in it, may need to go bigger. Mine had the super restricted 14-9 with the narrow intake- also now bored to 12mm.
You should be on the right track.