Google Sketch Up file : Bench
Although the first impression is that this bench is complicated, it is easily assembled with construction grade lumber. All of the joints are built in during the glue up. Its also easily customizable.
The whole assembly is based upon the two main rail assemblies. With through tenons, drawbored with 3/8" dowels, I don't see this bench coming apart anytime soon. The leg height is determined by your bench height preference, and the rail length, by your choice of top or space requirements. I chose a solid core door, which limited my length to 80". If you're using ply you can go a full 8'.
The center stretchers, along with the top, basically hold the side rails together.
The end caps are more than just about cosmetics. Remember that this is construction grade lumber. If things haven't come out so square, these can pull it into alignment and sturdy up any front/back wiggle. In addition, if you use any sort of end or wagon vise, these are necessary.
