i have learned that, yes it does make a difference, depending on what i am doing alsew,
i like to set my seams of HST, and yes, it may seam like an extra step, but it it sew worth it
to have it lay so flat, i use a Rowenta iron, with full steam ahead!! i have seen Eleanor Burns
do it many times and for her its no big deal, yes even my other idol Kaye Wood does it too.
so thats my opinion. good luck
katz