I fly sparge and can hit my numbers and volumes consistently by sparging and draining both HLT and mashtun till dry to get the preboil volume. I want to try and do a double batch this weekend and was wondering if I could keep my HLT full and hot as needed so that as soon as I hit preboil volume I can turn off MT valve empty Mashtun and fill with strike water from hot HLT to start next mash. What I am not sure of is can I keep sparging till I hit preboil volume and turn off the valve leaving water in mash tun? Is it the same as draining dry since it rinses from top down anyway or does that leave needed sugars and stuff from the malt?