This works for me and I'm doing a similar setup on a drop bar MTB conversion; quill adaptor, riser threadless stem and bar of choice.

Okay, so it's not pretty. Once I'm on the bike I don't look at it much. I used a tall Technomic on a previous bike and that took less adjusting to its looks but both approaches work fine as long as you get your rise and reach. Pretty is as pretty does.
RB-T Stem.JPG