Although regulation sized roll-a-boards will fit sideways, that means they take up the OHB space for more than 1-1/2 seats - 22" of the 31" seat pitch per roll-a-board. So obviously everyone can't stow a standard roll-a-board in the OHB's. NOTE: The same is true to a lesser extent for the bigger single-aisle planes. 3 roll-a-boards won't fit in the space above a 3 seat unit since the width of 3 roll-a-boards even wheels first is greater than the seat pitch in coach.

Jim