Anyway to do this with a custom parameter?
Setting the ROUND_XY_TO_GRID bit in composite glyphs causes components to be shifted by an integer pixel amount which preserves a hinted shape. This reduces file size so that when I use ttfautohint it does not need to rehint composite glyphs to create consistent rendering – especially important for glyphs such as super-/sub-script numerals and fractions which use components that are shifted.