If I am right, that wing has an upper and lower FG skin that's attached to a wood structure. If you have to assemble the wood structure, I'd replace all of the ribs that are to contact the rear tube and replace them with reworked ribs. Baring that, I'd install thin plywood doublers to the outside face of the affected ribs since you have the room to slide them through the structure.

UPDATE:
Just went to their website and found the structure is actually an interlocking design with the skin attached to it as I had thought. That makes changing out the ribs an easy task. I'd look at the inboard ribs closely to verify that they don't already have the modifications needed to install the tubes. If the modification is there, it's just a matter of assembling the wings. If the modification isn't there, you will need to replace the ribs. Just be sure to use material of the same type and thickness so everything still fits together properly