Hugh,
We did blast each other’s caps as far as possible but the only advantage that I recall was the obvious one of making it more difficult for your opponent to reach his immediate destination and of course you did get to take another shot. We had no numbers in the central trapezoids as you noted. As I recall we considered the lines of the trapezoids extending to the corners of the large box surrounbding #13 to be arms of a spider, the skull (13) being the spider’s head (ignorant we were of the 8 leg requirement of Arachnids!) Also there was no consideration of switching caps. Everybody played with their current favorite which was carried around in your pocket at all times. On occasion I saw “casual” players using unweighted caps or even wooden checkers, but they were generally considered to be fools or rookies. Thanks again for a great visit.
Jim Mason