Its nice having the riggers all the way at the back, but on that boat, with the rear deck, it would be a pain in the butt stepping up and down to set your riggers. I like them at the gunnels, just where the rear deck starts. That way your standing on the main floor, not bent over setting them up, and you can also lean on the rear deck step to help balance on a rough day. I find guys who have the riggers way at the back on a boat with a rear deck like that are on their knees setting the riggers. It wears you out after a while, especially if its rough.
A swivel base at the back of each track for the riggers, a couple ratcheting tube holders, and a couple salties and your good to go. Simple, effective, and no need to climb up on the back deck, or be bent over setting lines.
I personally like the riggers out to the sides. Spreads things out a bit, and leaves the back wide open for netting your fish too.
S.