That seems like a good way to do it but around here we can remember whether we are on the second lap, so there is no mark on the wire for 50+. Or at least most of the time we remember. I did play to 250 once on a set of 50 beads and that was a little harder to keep track of mentally.
We only separate 49 from 50 as a special marker if there is a scratch in the first rack. For a two-point foul on the break, 49 and 50 are slightly separated from the rest until the end of the rack in which that player scores some points.
If you want 100 beads, I agree with the comment above to put two wires up. I think it might be tough to keep them taut enough. Another way would be to put four wires up with 50 on each -- easier to support. You could do either left/right of above/below for the two scores. You could also score for four players in multi-player games.
