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: RIS #2: Pre-Prohibition Lager
Secondary #1: Blackberry Rhubarb wine #2: Empty #3: Cab MerMarqeNac Wine
Kegged: Two Hearts IPA, Pumpkin Ale
Bottles: Carmel Apple Cider, Big 50 Barleywine, Framboise Lambic, Barolo Wine, Berry Rhubarb Wine, Black Currant wine
On Deck: BGSA