By efficient, do you mean space-efficient, or do you mean a layout that allows the cart to actually collect wood faster? My setup is a zig-zag with two blocks of dirt between each zig/zag. It's quite large and the cart never has to wait, it is constantly cutting and shuttling wood back to the manager.
For now I'm just going to rework my fueling setup and start piping the secondary output from the sawmill (sawdust) to a compressor, then to the fuel supply chest. Hopefully that added fuel will tip it back to a slight log surplus.
Also -- I have an absolute glut of saplings (over 1000 stacks). I don't have the space to set up a biofuel system, nor the time or desire to convert one of my boilers to liquid. So is there something sensible I can do with the saplings? I was thinking about using them to fuel a generator supplying EU to the dedicated sawdust compressor. Could also burn them in the (steam engine powering) sawmill. I wonder if that will even dent my supply