Actually, none of the clothes converters work with scaling. (At least to the best of my knowledge.)

M2 comes with morphs like heavy, and the M3 morphs package includes a couple of heavy-type morphs -- some clothes have them, others don't. However, clothes converters can put morphs into clothing that doesn't have them.

If you are using scaling, is it applied to the entire figure? I've found no problem using overall scaling equally on both a figure and its clothes. The important thing to do is to scale the clothing after conforming to the figure. When you conform the clothes, it will reset the scaling.