pre-heat your MLT with the hottest tap water you can get. then dump that into a bucket (use it for cleanup later), and add the strike water to the MLT, and then stir in your grain bill.
minimizes the cooler from sinking a lot of the heat.
I lose 9-10 degrees doughing in my 5gallon MLT, and more like 14 degrees with my 10gallon MLT
the 10 gallon loses more heat during the 60 minute rest, due to more headspace. the 5gal loses 1-2 degrees tops.
I mostly use the 5gal since I don't make real big beers. but i have the 10gal for when I do
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10