Originally Posted by grolby
Well, MTB and road bars are different diameters (I think road are 26.0 mm, MTB 25.4 or 25.6?), so even if you get it to work, it won't be a perfect fit. Just switching to drop bars may mean a new stem - this isn't as minor a change as it should be, sadly.
The diameters you quoted are ONLY for the part of the handlebar that the stem clamps onto... it's a little narrower everywhere else.
I forget the exact numbers (sydney? sydney?), but it might be worth trying. A shifter isn't a safety-critical part, so I would not hesitate to try spreading the shifter clamp a little or using a shim to fit the shfiter pod onto a drop bar.
I wouldn't do this myself, however, because I think you would find the shifter position annoyingly inconvenient. My favorite drop-bar shifters are bar-end shifters. You can get an old pair that will work in friction mode for a few $, or ~50 for a pair of new 8/9/10 speed Shimano bar-end shifters.