Below is a fit chart for the Speedmax measured to the rear of the pad. The number in brackets is the pad spacer required. Each size fit range based on using stock stem.
On the XS you would drop out the big spacer (so the top of the stem wouldn't match the top of the bento, though I heard rumours of a lower stack bento) and just stick in a 5mm spacer
the PD pads move in 7.5mm increments of X so you could hit 395,555
If your padx in the fit report is to the rear, you're probably better to look for a different bike (like a Fuji Norcom Straight) that is longer reach.
Speedtheory | ST Interview