I have had success with both 5"parabolic and shield cut. It is possible so don't give up. There is a sweet spot and you need to find it by inserting a feather in the clamp and with bar moving free, go back and forth looking at the leading and trailing edge to optimize position. If you have not tried Saunders NPV glue, you might try that. It is very good....dries clear...and sets up in 15 minutes. You will end up with plenty of helical....also...line up your rear feather with the same side of each clamp...so if you index off the left side of the clamp, do that and be consistent. I also number each clamp and use that clamp in the same position each time and that ensures a good consistent result. Hope this helps. Chuck