I have a mtb I rode for years with what I thought was very good fit, and decided to build a road bike with drop bars, using fit on mtb as a design guide with a few tweaks.

Now that the road (touring, actually) bike is built and mostly fitted, I find the the ETT length + stem length is 7cm shorter than that of mtb, but the distance from saddle top center to normal hand position (on hoods on road bike) is within 1cm on the two bikes.

I'd need to lop off 7cm of stem length on the mtb to fit the same drop bar in place of flat bar, which is nearly impossible since I have only 11cm to start with. I'd need a very short, steep stem to make this work. I predict you'll need the same, something like this:

http://www.aebike.com/Dimension-Thre...8_p_26022.html

You may also need a short reach drop bar too, to match the reach with flat bar.