Originally Posted by Spoonrobot

Did you buy a stock mountain bike and add the drop bars and other required parts?

Yes, I took a stock 9 speed 26" hardtail. Removed the stem, handlebars, hydro brake calipers, shifters and brake levers. I added a new, short stem, shifters and drop handlebars as well as mechanical calipers.

Did you build from the ground up?

No

How does the riding compare to a full-fledged mountain bike on gravel?

The varied hand positions are the biggest improvement. Instead of 1-2 positions I now have 4-5 as well as being slightly more aero overall. It feels significantly faster on the flats and rollers but gives up some speed on single track and long windy descents or anywhere there is really loose gravel due to the decreased leverage from going to 680mm wide flat bars to 460mm wide drop bars.

How does the riding compare to a rigid-cross style bike on gravel?

Front suspension fork makes rough gravel and descents a lot more comfortable and significantly faster than my rigid cross bike. The geometry difference and wheelbase makes it slightly less responsive and it seems to climb slower, even with the fork locked out. I also noticed the gear and wheel size difference appear to be slightly slower as well. I think the wheelsize difference creates a lot of the differences I've noticed, a 26" 55mm wheel/tire combo is very different than 700cx35 or 700cx40. Still figuring this one out.

Suggestions/tips for sizing?

Buy a frame/bike with similar top tube length and make up the difference in overall reach with a shorter stem. The reach between my road/cross bikes is about 10mm shorter than my drop bar MTB but the stem difference is 50mm.