You can change the Hotbars to be almost any size and shape you want with the default UI. Just unlock them (if locked) and drag the corner to a new size.
For example, I use a 2x6 hotbar on the lower left and a 1x6 hotbar above the main chat window. All done using the default hotbar UI piece. The photo below shows my custom UI but that piece is not custom but from the SOE default.
See:
You see the hotbar in the lower left? You can drag your hotbar to look like that with the default UI. You can also make it 1x6 or 3x3 (I think) or several other combinations.