i have a rule- if you run more than 30mm of spacers, your frame is too small. i've done it before on past bikes, but no more. i feel so much better when my back is stretched out. i tend to roll my shoulders forward if the bars are too high and end up in pain either during the ride or right after. i finally cut the fork on the mr pink today. don't plan on running any more than 10mm under the stem.