Setup for a full body portrait on white bg?

Remember that the white background is a light source. As it gets brighter it will overpower the sensor and cause clipping. That's not necessarily bad, but it has to be controlled relative to the subject.

A good rule of thumb to use as a starting point is the one Zack points out; set the background lighting, then read it as a light source from the back of the subject. He suggests having it read the same as the main light. This helps to determine how far from the background the subject has to be. If the background lights read F16, then to get the background (as a light source) to read F8 the subject will have to be farther away than if the background lights read F11.

F8 for the subject and F11 for the background may not result in white. If its necessary to set the background at F16 then the only option is to increase the exposure on the subject the same one stop more or get them farther from the background.

That works great if you have the space, but in my situation, I barely had Maybe 10 feet of length to work with.

I have managed some full length shots in a small space using a Lastolite Hi-Lite background and some white tile board from a construction store like Home Depot or Rona. I raised the tile board "floor" up a bit by placing the tile board on a couple of pallets.

Smaller space means there will be compromises.
Using something that is translucent and shooting the light through it is one approach. There is a potential problem with full length for the "joint" with the floor. With the white paper the seam becomes almost invisible by overlapping away from the camera. Sounds like raising the board a bit works too.

I've done head shots with a translucent popup diffuser about 2 feet behind the subject. No reason that can't work for full length. The trick will be getting the light more or less even across the panel.