I had extended my HQ16 from 6 or 8 ft [I forget which it was] to 10 ft with no problem.
I strongly suggest you call HQ for direction. I know I'd rather have poles/rails that go with the machine for better performance. HQ phone tech has always been helpful for me. We even once had a phone conversation and the a cell phone photo sharing to resolve an issue when I updated the bed and trolley/carriage. The problem was a contact in the trolley wiring connecting to the machine.