I discovered I was being quite silly and inexperienced with reading patterns--I thought "actual bust" was what my size was, and "to fit bust" was the size of the cardigan. It actually has 2 inches of ease, as opposed to the 2 inches of negative ease that I mistakingly thought it had. I just followed the pattern (i.e. my bust is 36", so I'm making the cardigan 38"), except I made it nip in a lot more at the waist (ooo la la!). I never knew knitting required so much math!
Fortunately I did do a gauge swatch, but I'm not really familiar with how stretchy it is, qualitatively, since I've only done hats and scarves and never really cared about stretch. It's in stockinette, with ribbing on all edges and up the sleeve seam. Do you think that'll hold it's shape ok or start to droop like Dali's melting clocks?