I have an Avistar that was terrible on the runway in a take off roll. It was so difficult to steer and take off my instructor had problems. I had already made 10-15 landings before we made some adjustments in the engine incidence. We found that the engine was pointed down 4*, if you have had trouble and damaged the firewall on top of it this could be the problem. We reset the downthrust to -1/2 to 1* and right about 2-3*, it flies great now and the takeoffs are much easier.