Those of us who use XeTeX directly (not through Paratext Print Draft) usually use a command like this in the setup file:
% make sure multi-line \mt1's have enough space between the lines
\sethook{start}{mt1}{\baselineskip=22\FontSizeUnit\relax}
I imagine if you put this command in your PrintDraft-mods.tex file, that the multi-line spacing in your \mt1 titles will be “different” - maybe not what you want, however. Then you just need to figure out what number to use in the command instead of “22” (which is a multiplier for the FontSizeUnit) to give you the spacing you want.