How does the inside diameter of your tube compare what your trying to match? Looking at wall thickness of those tubes it seems to be overkill for the application your doing. I suspect that if you started with a larger diameter mandrel you would have more room on the inside of the tube, a thinner wall, and ergo less stress on the plastic when you insert the jig head. Thats my SWAG. (Scinetific Wild @$$ Guess).