Thanks for all the positive comments.
I made the collar about 12 inches high so that I could put 2 kegs on top of the bump in the floor caused by the compressor and still have the quick connects clear the lid of the freezer. This allows me to get 4 kegs into a small footprint.
I am about 6'2" and never thought about having a problem placing full kegs inside.
I used some generic foam insulation I bought at Home Depot. Two plys of 1" foam with an R5 rating each.
I thought about using double sided foam tape to fasten the collar to the freezer, but it fits so well without it, that it is just setting on top. A small lip on the freezer and its mass keeps it from moving. I ripped the mdf and foam using my table saw without changing the setting. The foam was slipped in place after the assemble mdf was placed on the freezer. They effectively translate the profile of the freezer top to the top of the collar. The lid fits very snugly. I can take the collar off easily to move the freezer or even load in Cornie's.
The lid is attached with a few wood screws into the mdf.
Now I just need to fill it with beer!