jetting for exhaust restriction?

There's a big open space behind my apartment complex that I want to use ocassionally for a quick joy ride on my CR250 but I don't want the neighbors to sic the cops on me. So I want to block the flow of exhaust half way thru the silencer and make the exhaust travel thru new fiberglass I'll lightly wrap around it. That will create more exhaust back pressure which should make the engine run hotter. Normally I prefer quiet bikes anyway and may just keep the silencing mod if it don't stifle the power too much. I may switch to using metal scouring pads instead of fiberglass to allow more flow. It depends on the resultant sound level. So what kinda jetting changes should I expect to have to do?

Hey, if I find a way to have a much quieter bike then it may inspire others to do the same which is needful for our sport. Such a modification was mentioned in the Two-Stroke TUNER’S HANDBOOK By Gordon Jennings.

hey, that's a cool gizmo. I may make something like it myself. thanks