looks like we have the same rig so I'll take a stab but I don't know what kind of frame you have. Do you mean centered or balanced? I can't say I've ever worried about having my weight centered in the boat but I don't want to be nose or tail heavy.
I've got the NRS frame and I do the same thing, I like to have my legs out straight which gets my knees lower for the return stroke of the oars. Some of it depends on which seat you have and oar stands. I went to the taller ones and those helped quite bit and I've tried all the seats. the low back is shallower so it doesn't push your knees up like highback does. Most of the time I sit on my dry box though which is a fairly tall one so I'm on the edge. For multi-days when I don't have the fishing setup on I run the standard table/drop bag, cooler, rower, dry box setup. In a 14' boat this does get a bit tight in the back but I've never had to stack things real high in the back. I've felt the same way at times that I should be utilizing that big rowers compartment a bit better but you can always fit at least a couple bags down in there on each side or under your legs. so far been fine on week long trips with a couple adults and kids. although, to be fair, I've got a big group so I don't end up carrying much of the kitchen gear, etc. I can go self sufficient for 3 or 4 days though. Every year I tweak it a little more and packing gets progressively better every trip you do, you can definitely make it work.
I don't think I have a great pic of that current setup I just described but I'll look.