You will have heat loss but I don't think it's an issue. You might consider rice hulls if you crush on the fine side, the pump can pull a suction under the false bottom if the bed gets too compact.
I recirc the entire rest period (I use a copper coil in the mash tun that circulates HLT water to maintain temps). You should only need to recirc about 10 minutes so any heat loss is not a bi9g deal since you will be boiling it shortly there after....
Love Montana, I need to find a way to make a living in Missoula !!
Something is always fermenting....
"It's Bahl Hornin'"
Kegged: Sour Saison, Pale Ale, Aggie Ale, Firestone DBA, De Koninck Blonde
Bottled: Belgian Quad (Grand Reserve), Derangement (Belgian Dark Strong)
On Deck: Pliny the Younger