Two stroke engines make compresion on the up and the down stroke. Shaving the head (or swapping the head for a 'high compression' head) is only half the solution. You need to add what used to be called a 'stuffer box' to the bottom end to complete the solution.

A properly done 'porting job' will work wonders to get the powerband in the RPM range you need. On the older Mac engines you could also add multiple carbs by adding one or more carbs to the bottom end. Three lifetimes ago (back in the late '60's) I had a three carbed Mac 75 that came off a racing go-cart that was clocked at 90+ MPH. I wanted to add a 'pull-start' and made a 1/8" spacer that I installed between the head and the cylinder to lower the compression. I wasn't aware (at the time) about the lower end compression and the 'pull start' would barely work because of the high compression. I also removed two carbs from the bottom end, as I was installing this engine on a mini-bike I had made for my son. Ended up being much too fast for him.

Contact someone that is familiar with building racing two strokes for additional info.