I am not affiliated with any of the stores; so this is just how I use it. I believe the plastic cap was intended to be mounted in a case, and the bevel line would match up with a manufactured case edge, so it would stay in place. I think it is an important part of the kit but only to protect the helix antenna from potential chipping on a flip.
I use mine, however, as a functional part of the mounting of my GPS. To mount my u-Blox, I put a diagonal slot in the upper deck (see my photos at http://diydrones.com/photo/underside-of-upper-deck?context=user and I think you can see the GPS in one of them) This is a tight fit, and it holds well under friction, but it is not enough. I have CF posts that rise up above the plate, protecting the battery (on top, not bottom, in that design) and the GPS antenna. I place the plastic cover over the antenna, then use a small rubber band (quick) or zip tie (when I do not plane to remove it in the next few days) to wrap from the bevel on the cap to the CF rod. This acts to keep the antenna cover on, and keep the gps unit firmly in its slot. No pressure is put on the PCB or GPS unit, hanging below, and the CF rods prevent any kind of sheering.
My quads might be rough looking, but they are all rapid prototypes. If this was all done in carbon fiber, with a black zip tie I think it would be quite nice looking, although I have not yet given much though to aesthetics. That specific design was intended to emphasis DIY easy-of-use, the components are widely spaced, easy to remove. The entire central column comes out quickly, and reinstalls quickly and consistently for CG/alighnment, and, specific to your question, the GPS unit is very accessible, easy to remove, but secure in place. The cap just keeps it from moving away from the rod, opposite from the opening of the slot, where it could fall off the plate. I can access the programming pins (not yet soldered in that photo) to load AssistNow data w/o removing it from the quad.
Just one example of how another amateur uses the cap. I do not glue it into place.
Thank you for your reply. ..very interesting implementation. ..makes a lot of sense that they would just include the cap since it is needed for protecting the antenna, and is probably meant to be mounted in some kind of plastic kit box or something. In all, I guess it is ok to experiment with implementations for each project - but the cap is needed to protect the antenna.
Hi Paul, we did check with the supplier about this issue, but from their reply, the cap is still within the manufacturing tolerance. Basically, the not so tight fit shouldn't be an issue.