Go to home depot and get an extendable painter's pole. They go from 7 feet out to about 13 or so. Add a few of the large spring clamps and you will be good to go. I use this anytime I am on location. One tip is to hold the pole up to the top mounting stud and then clamp the pole and the stand together. Much sturdier than any other setup. Get an extra clamp or two to keep your seamless from unrolling.
If I only need a four foot seamless, I use a five foot piece of PVC, which stays in the box with the seamless.