As stated above, it depends on which model aircraft. Your comment about the "single seat" side suggests you MAY be referring to the EMB-120 turbo-prop. If that is the case, be aware that the single-seat, "A" side has immovable armrests and is very tight. Most "B" seats, on the other hand, have a movable armrest on the aisle side and can be a bit more comfortable for large passengers. I am not as large as your friend but have found that rotating that rest up and out of the way makes it easier to leave the center rest down by allowing me to slide over an inch or two, slightly into the aisle. To get that armrest to move, you reach under it at the hinge point, where you will find the release catch switch. Holding that in allows the armrest to rotate up.