I can do doubles pretty good with socks.. i tried in several types of shoes and i'm still looking for ones that will let me. The issue with the technique it think were both using.. (look at my video if you want to see it, I'm not here to repost) is that i arch my foot a bit for my heel stroke behind my pedal. with shoes being flat and not allowing my foot to bend i cant get it as easy.
also. with doing double strokes at VERY fast speeds i like to FEEL the hits... shoes make it harder to do so.
i played in shoes live and socks in the house for the first 12 years of my drumming i would say over the last 3 years I play in socks and I like it al ot more.
shoes give you WAY more power in your stroke too though if find.
boating shoes / those individual toe shoes are the next two I'm going to try