I know this is low-tech, but it works just fine. Stainless steel hose clamps are used to attach the driven element halves to the PVC cross which acts as its support. This has the added benefit of allowing you to fine tune your antenna for lowest SWR simply by loosening the hose clamps and sliding the halves of the driven element either closer or further apart. Figure 1 shows the method used to attach the driven element to the PVC cross. Others who have duplicated my design have used self tapping screws to attach the elements to the PVC crosses and tees.
Performance is the same using either method.
The screws are much less expensive but they do not hold the elements as securely. If you wish a slightly neater looking beam, use the self tapping screws. If you do not mind spending a few more dollars for the hose clamps, use them instead. If I were to build another beam I would use screws for the director and reflector, and hose clamps for the driven element. That would give me the best of both methods.