I'm currently making a fleece TQ with a weather-shield mystery fabric sewed on top. Rather than sewing the footbox, I decided to use a draw cord and possibly buttons or snaps to connect the edges up the TQ about 16-18 inches.

My thought is that when the nights aren't cooling down too much, I'll just use it as a flat blanket, but when the nights are cooler (spring and fall) I can synch up the footbox.