That sounds very familiar. Although the SuperNovak speed control is a good one - it certainly is not perfect. Although it has a "boat mode" where it allows 25% power for reverse, I have the same problem. The SuperNovak is really designed for cars, and therefore has a "brake mode", so when you reverse the first time from forward, you will likely have no reverse response. The second time you reverse, BOOM - there it goes!

I deal with it by being very light on the stick and just giving 1 second reverse holds - - anything other than that will likely be too much!