Suncamp Ultima 390 Awning - rear upright poles

Has anyone found an easy / effective way of keeping the rear upright poles firmly fixed - and upright?

The instructions simply say

"Finally, fit the two adjustable rear support bars, one to each rear corner of the awning. The pole’s flattened top section must be inserted into the reinforced retaining pocket found at each top rear corner, behind the triangular reinforcing panel. Both poles should be extended then locked by turning the lock screw clockwise."

Easier said than done, as we find it difficult to extend the poles sufficiently so they will stay firmly in place.

Thanks, Shelley