Moccasym Splitter Sizing

Not a new question: how do you size your moccasyms for sandstone cracks?

For cracks I'm currently in a size 10 Anasazi VCS (10.5 street shoe) that leaves a little play in the heel cup, but the shoe is tight on the Achilles and snug in the toes (but not curled). What do you think? Same size for the mocc? Half size down?

I got a half size down. They stretched and now fit perfectly. I feel like they'll be too loose if I got my street size. There's no laces or velcro to latch them on to your foot, so they better be snug to stay on!