Well, now that you mention it, the length of my little finger in particular is probably what's causing the difficulty. My hands are a little on the small side, and in addition, my little fingers are about a half inch shorter than they ought to be.
I have given up even trying to use the finger rests, it was too much of a stretch for my poor stunted little fingers (and I'll be needing them free for playing the buttons at some point anyway, right?)
I also have wrapped a finger cot around my thumbs to make then a little fatter, even with the thumb straps tightened up all the way, my thumbs kept sliding too far through the straps.
Back to practicing...
Much thanks,
Susan