I presume the carboy / bucket has to sit on the hump? This is the reason for the 1 foot collar?
the advantage to the collar coudl be that you can ferment up to 15 gallon batches in one of these then (brewshops get their malt extract in these containers) 14" diameter and 26" tall without airlock
The lid closed on the fermentor with no room for an airlock, so I needed a collar and my neighbor gave me a free 2x12. The goal for this one was cheap yet functional so on it went.