As Bo said, every builder can make his own improvements if he thinks it is necessary. But before extending the secondary spar and wingtube please analyze the examples below and compare them to the Vortex wing. Both are top, proven designs, already on the market for a couple of years.
The first image represents the complete wing structure of the Naruke Ascent monoplane right before adding the balsa sheeting. Here are the main differences to the Vortex wing:
- Ascent doesn't have a secondary spar to reinforce the wingtube, it only has 2 stringers not connected between them or to the wingtube. Vortex has 2 stringers at the top and bottom of the wingtube and 6mm balsa shear web in between which creates a strong secondary spar;
- Ascent wing root rib is made of balsa, the one on the Vortex is made of 3mm liteply;
- Ascent root rib has only a plywood roundel as reinforcement, while the Vortex has a doubler that connects it to the top and bottom of secondary spar;
- There is only one other rib doubler on the Ascent (near the wingtube end). All 4 ribs on the Vortex have plywood doublers.
The second image shows the wing structure of the Neo Stage which is also sold as a kit in Japan. The structure design looks similar to the Ascent. There are probably dozens of these models already flying in the world, so the structure is obviously strong enough for F3A flying. I am only trying to say that the Vortex wing is overbuilt by comparison, so please make sure you are not trying to solve a "problem" that doesn't exist.
I would strongly advise against cutting into the main spar to make room for the wingtube in an attempt to join the 2 spars. This would create a weak point in the main spar which can affect the wing structure.
