First off I find the Simples to run True to Size so yes, 37 would probably be better. Also with any heel height 100mm and up it's always best that they fit tight so the heels don't slip out. CLs have been carefully constructed to work with the physics of a females foot to reflect the ideal angles of the shoe for standing and walking so it's essential you have the right size otherwise the mechanics are out of whack and you may find it difficult to walk or they may cause you too much pain with prolonged standing. But if you're stuck with a pair and have to use insoles, use the front/ball of the foot ones...these push the feet back against the heel. Most people make the mistake of putting heel grips in, but these push the feet forward into the shoe even more and can lead to even more heel slippage. Also try taking a cheap shoe insole and don't be afraid to cut it into whatever shape you need. I did that with one pair where I cut the insole to fit right near the tips of the toes....almost like a little faux-wall at the toes which then pushed my whole foot back.