I was thinking as I typed, literally the idea came as I was typing the post. Any round bar would be ideal with a stop on it with maybe one or two little improvements. The stop would be a fence type stop with some length to it for stability especially when using the first set stop as a story stick for the second. Chasing a round stop and bar and trying to hold it while setting the second would get old fairly quickly. Beyond that I don't think that you can beat simple and it sure would be cheap but more importantly accurate. I have always stayed away from track saws for the simple reason of setting the track to an accurate and square dimension but I might buy one now.
Chris
Everything I like is either illegal, immoral or fattening