Yes but it gets very narrow. I have looked at building a custom bag but in the spirit of making the bags even on both sides you would need to build shelves due to height variances in the lockers.
Adding all of those ballast bags to the existing pumps would put a lot of pressure on the pumps once you started filling the overflows. Not to mention that unless you wanted to fill all four every time you would need to install ball valves to close off individual lines going to the extra bags.
I just think its a cleaner install and faster fill and drain to put in two more thru hull's with pumps.