40 is pretty cold for even lager strains of yeast. I would insulate the fermenter as well as possible inside the chest freezer to maintain the beer temps more consistently. Wrap in sleeping bag or something similar.
Bigger question is: if you have a temp regulator on your chest freezer, why not bring it inside? Or at least garage where it might be warmer? Would make a perfect lager.
Primary #1: Empty #2: Empty
Secondary #1: Empty #2: Black Currant Wine #3: Empty
Kegged: Umlaut my Kolsch
Bottles: Big 50 Barleywine, Framboise Lambic, Russian Imperial Stout, Barolo Wine, Berry Rhubarb Wine
On Deck: Dusseldorf Alt III, BGSA