I'll try and type faster tonight.
The tower I installed is a 3" tower with a 4 1/2" base with 4 bolt holes.
The 4" I was referring to is really 4 1/2" and it's on the inside of the fridge. That's where the coils are so that's where I concentrated my effort.
Pierced coil equals end of project. As soon as you open the door look up. It's the closest part to the front. It's the first section of white plastic.
Where the ceiling drops 1/2" that's where the refrigeration coils start.
DO NOT DRILL INTO THAT PART UNLES YOU REMOVE THE TOP AND LOCATE THE COILS.
pic is of the ceiling of the frige.
The next pic is of the top of the fridge. I put the front of the tower where the the black top changes from motteled to glossy. The line is very apparent.
You can see in the next pic where I traced around the base and marked the holes. I think it's prudent to mention that if the base has more than 4 holes, measurements should be taken to ensure that the bolt hole located in the rear don't line up over the coils. You can see in pic 1 there isn't a lot of extra room.
The final pic is a close up of the hole. All I did was find a scrap piece of pvc. Mine happened to be 1-1/4". I found a hole saw the same diameter. Driled the hole, cut the pvc to length, inserted, and caulked it on top and bottom to maintain the vapor barrier.
As for the temp control. Yes, I did remove the light and turn it around. That little extra space allows two cornies to fit.
As Elmer Fudd said, "Be very careful of the copper tube attached to the temp control." If it kinks or breaks you'll have to use an external temp control.
One final comment. Everyone has there own Ideas and preferences. Some want to have 10 kegs going at once. I would love to have more but I don't have the space. I live in a tiny house and have to have a tiny fridge. Therfore my fridge is perfect for me.
Hope this helps.