I try tell short how my only first and last MuN-pipe is done.
I have calculated pipes with many programs, but some year ago i purchased Mota-program. After long and busy working a planning was ready. I get lot help of my work (CAD-man) for cones. Then cut piece of 1mm plate and welding then together.
There is graph where you can see difference between Mota and real world. Anyway, i like Mota.
I think stock "modern" KX500 have exhaust KIPS close below 170 deg, KIPS open below 190. Transfers about 120 deg.
My stock old -86 main exhaust (no KIPS) was 181 deg and transfers 123. Now exhaust is about 195 and transfers 134. MuN-pipe needs so high transfers, so that is rideable.