Well, good luck. I'm happy with fermenting 4 gallon batches in 5 gallon low profile kegs. They've got a bit better of a fermenter geometry than standard kegs. That is, if the fermenter geometry theory is to be believed for the taller, slimmer fermenters...
I like being able to move my beer under pressure to the serving keg and I never have to open the lid, unless I dry hop.