I started on the coffin part of the bar; pictures below.
So, the main idea behind cooling the coffin is to use a fan to create a negative pressure on one side of the coffin box by blowing air from the box down into the freezer. The low pressure on the fan side of the coffin will pull air across a channel (constructed out of insulation foam) and up through another hole on the other side of the coffin (the pics will make things clearer). The beer lines will be fed up and routed through the high pressure side of the coffin thereby, in theory, cooling the lines and the exposed shanks as the air flows across and back down into the freezer.
I was going to use some flexible dryer duct hose to pull cold air from the bottom but on testing the setup tonight, I get plenty of cold air blasting up through the high pressure side.
It was a bugger cutting the holes through the sub-top down through the freezer lid but they turned out ok. My fan is a 120mm Antec computer fan with 3-speeds. 4 inch, Schedule 40 PVC pipe is the perfect size for this fan.
The pink foam is rough cut at the moment. I will go back behind, seal all the inside joints and cover surfaces with silver ductwork tape just to add another layer of help in keeping the cold in and the hot out.
Tomorrow night, I'll make the top of the coffin, cut the shank holes and start work on a removable back cover.