I measured a 50M rod out of curiosity. It looks like the taper goes all the way from 0.050" to 0.038-0.039, and there is only a small step to 0.036". Does this sound right? If so, I wouldn't think there would be any major difference between a 50M rod and a custom rod that tapers all the way to 0.036". As Kenth said, the taper will be steeper, so it will be slightly richer at every point along the taper, but not by any significant amount, IMO.