Photo showing wing joiners, and the larger one is 7mm carbon tube and the smaller is 4 mm. I have extended the 7mm to go through the dihedral joins on both wings and this was where the long drill was used. The 4mm only goes as far as the dihedral join but still needed a longish drill. This shorter drill was made by using a 2mm bit pushed into the carbon tube to make a pilot hole in the ribs then followed up with a 4mm bit i had tacked on to some 3mm rod that i use to replace bent motor shafts. Most of my motors now have 4mm shafts and these don't get bent. The original 4 mm joiner was only about 70mm long so i now have a rear spar in part of the wing at least. Have added some hook and loop to secure the wings to each other but this is probably an overkill. The 7mm tube came from Hobby Hangar and the smaller 4mm came from Rainbow Flight,Nelson kite shop.