I'm not sure why you would mix the two but what do I know. I've only handquilted and never tried to machine quilt. After I take the time to really baste the quilt sandwich and get it into the frame I'm not taking that sucker out until it is done.
I'm sure there are a lot of better opinions on this than mine. My $0.02 US is that handquilting "drapes" differently than machine quilting so you might want to take that into consideration. There are some battings that are harder to hand quilt than others.