I don't see the need for pre-bending flexible plywood when it has to get bent again, all that flexing around probably won't be a problem but doesn't seem like it'll do anything without a form holding the curve. Once the glass is on, tack free, then another fill coat applied, wait 'till it's tack free then put it on. If ring nails or screws are used you should pre-drill the holes because the glass will pull away when the nail is driven through the wood.
It's fun trying something new and finding it work out ok.