Question about incubator temperature swings.

My title isn't very descriptive. I didn't know how to word it in just a few words. I have an old discontinued gqf cabinet incubator. 1200 series if I remember correctly. I have it in my garage, which is not insulated or heated. I have hatched one batch successfully and have my second batch in now and they are doing good as of day 14 candle. The dilemma is that I get temperature drops in the night when the outside temperature drops. This morning it was 97. I don't think that is killing anything but I was thinking it might be delaying my hatches. I was thinking about building a box big enough to put my incubator and seperate hatcher inside that I could insulate. I can't insulate my whole garage for a two degree temperature drop in my incubator. I think the incubator will give off enough warmth in a smaller area to regulate the temperature better but I am concerned about the ventilation with this idea. If I make my vent holes too large then it defeats the purpose but too small and I don't get enough oxygen.

Has anyone done anything like this or do you have any advice? Or I might just be over thinking and I should leave it alone. Thanks for any advice or ideas.