Normal configuration is two riders: a 4.5 year old harnessed in a frontier 85, installed with latch; a 22 mos RF in a marathon 70, also latch. Both kids outboard. I'd like to keep these seats but have an alternate configuration to accommodate an occasional HBB in addition. The seat is pretty flat, and I was able to install the frontier closer to the door and get the rf MA center with a belt install. Both seats rock solid, but they don't puzzle well in that the frontier which is so wide shoves the MA about 1 inch off-center. Do I even proceed further with trying to fit the booster or is this a no go situation?