Hi Moe - good idea to add more insulation over winter. We've not got direct experience with this, so if you come up with a sneaky / ingenious solution, do let us know!
Well, I've had a go and just put some down the sides, the light bars hold it in place quite well. Jammed some over the door on the inside and between the lid and the sides. So far looking better than last night according to the data. Will know more in the morning but it's not a straight drop to 5⁰C like last night.
Can you use a some sort of clip into the frame?
Inside or outside?