What I would do (YMMV) is tilt the saddle back ever so slightly, so that your hips are firmly planted on the seat and not sliding forward constantly. I think having them anchored is important. Might make riding in the drops less than ideal, but it's what i would do, FWIW.

Also, I have done a couple MTB to drop bar conversions, and found it impossible to get comfortable on them. Thought it would be a cinch, but it was anything but, and finally gave up.