You're putting an OS 91 two stroke in a Sig Senior Kadet. WOW!!!! I think your problem isn't going to be fuel tank lines, etc, etc. It's going to be slowing the plane down enough for landing. You might want to consider swinging a very low pitch prop with that engine. I've flown two Sig Senior Kadets, one with an MDS .68 I think and one with an OS 70FS. They both floated and floated and floated. The Kadet would probably fly fine with a .46.

Good luck,,,,,let us know how it turns out.