RE: Conversion from rubber bands to fixed wing
That OS 70 is going to be alot more power and stress on a trainer airframe...as for you wing, you might look at the Dubro nylon wing mounting kit and some hardwood blocks. Check out their website. I converted a rubber band held wing to nylon using two of these kits. However, my plane was built up so I did not care about damaging the covering material and I had plans to figure out where to put the mounting blocks inside the wing. I set mine up were the bolts mount flush along the airfoil line. So the thread blocks were angled inside the fuse.
It's probably best if you get someone with building experience to help you.
Mount the thread blocks to the plywood structure of the fuse. Depending on how you orient the thread blocks will also align the bolt path through the wing. I found it easier to mount the thread blocks first and start for the rear of the wing. Make sure the front mounts dont interfere with main spar box of your wing. Cut the head off an extra nylon bolt (leave it long) and sharpen to a point. Then thread it in so the sharp point is out barely over the saddle to puncture a hole in the wing. Align the wing, make sure you have equal distance all around. Then press down to puncture a hole in the covering. This will be your starting point. Drill the hole through that bottom only then run the bolt out just enough to puncture the top sheeting of the wing. Drill that out through the bottom. You should now have a hole to run a bolt through. Now repeat the other side but with the bolt in the new hole as this will help align the wing. Do this for the front, just not too close the the main spar. When all four holes are done. Take measurements of each hole top and bottom. Its time to cut into the wing. Find the nearest wing ribs as these will be the places to glue the hardwood blocks. The sparbox is also a good place to glue the front blocks. Since its a trainer, its flat bottom airfoil makes a good reference point align the blocks. You are going to have to shape the blocks to fit, mark the new bolthole from the top of the wing. Once you have them shaped, sit them on the wing saddle and mark the centerline of the thread block along the hardwood block, this is now your drilling angle. Drill your holes, trial fit the blocks and bolt them in without gluing. Make sure the wing mounts flush to the saddle and is still in alignment with the rest of the plane. When its all lines up, glue the blocks in and cover the exposed areas on the bottom of the wing......
Its a bunch of work, but no more rubberbands. I really do recommend you get someone to help out. Have fun!!