I had that problem with my gracie frame. It also was extendable, and when I went from 8' to 12' - it came with one 8' pole and one 4' extension pole. I had DH make me a wood spacer that held the front and back poles the required distance apart, it wasn't the best solution but it worked. I removed it for each advance, and then put it back in place to sew. That was with the Bailey, and it liked a tight quilt. I now have a fixed 12' frame with an HQ Fusion. Those poles are very ridged, even though they come in three 4' sections. Once put together, they don't bend towards each other at all.
Another idea is if you can put a sleeve inside the pole to help stiffen it up. Would depend on if it's hollow, and you can get something that is big enough to barely slip inside - especially if you can bridge the join point.