I'm 5' 4'' and can use the large though its definitely longer then I would prefer. I didn't keep it but if I had I would have added some snaps or aplix to the tail so I could shorten it when I used it and lengthen it when dh used it. You could just put a couple of snaps at the very end and then the other snaps higher up to temorarily shorten the sling for you. You'd have to be careful that the snaps or whatever where still low enough that your dh could tighten the sling without interference.
don't know if this would work just my rambling thoughts. I think if I were you I'd e-mail mayawrap customer service (or call) and tell them your measurements and see what they say.