Come on Jimbal. I don't know how many years you have raced 1/8th scale but I've been at it since Kyosho made the Burns (God I'm dating myself) LOL It wasn't even a Turbo Burns
Maybe I've been lucky or something and even though I have heard of it happening I have NEVER had a rock stop my flywheel in all those years. Putting a bevel on the edge of the chassis at the flywheel opening if done correctly is the easist way to fix the starter box issue. Beveling the edge of the starter flywheel is only one of the problems. Most starter boxes have a relativley large diameter wheel and it simply won't get up into the flywheel opening easily without a little minor cosmetic surgery
I'll try to post a picture of my modified chassis later