I’ve always flipped the feet. Only recently have I begun trying to roll the toes over, and while I would really like to keep with this, I find that, in Chaturanga, while my elbows are right over the wrists and I execute Urdva Mukha Savasana, I cannot roll over the toes without ending up in a too-long Adho Mukha (feet and palms too distant)…so I end up having to step an inch or two forward afterward.
I cannot slide the tops of the feet forward an inch or two in Urdva just before rolling over the toes as I will invariably bunch up either my towel or the mat or both, no matter how much weight I apply over the wrists to reduce the friction of the tops of the feet on the mat. I find this “sliding” works for me very well only if I’m directly on the floor but I won’t do that with any normal practice.
I’ve tried all manner of variations of Chaturanga, such as shortening/lengthening the distance between toes and wrists to eventually emerge into DD with (what I believe) is a correct distance. I don’t believe my stance in my DD is necessarily too short, because if I cycle back through Dandasana and repeat, every cycle creates another inch or two distance and eventually I’m lying prone!
What I’m thinking is that my toes aren’t sufficiently forward and my heel’s aren’t sufficiently back when in Chaturanga, likely due to lack of hamstring/calf flexibility.