There is a problem with attaching a glider rack to the front of the newer cars - there is nothing solid up there! Just plastic.
This shows my solution for the main load path - hardware store hinges that can fit in the space between the hood and fender. The hinges are attached to the main structural cross member (that supports the radiator, etc). Without the rack the hinges fold flat beneath the hood and are not visible. To attach the rack the hinges are folded upright, and the rack supports attach with countersunk screws and wing nuts. Bits of duct tape on the hinges help protect the paint.
The hinges will only support a vertical load, so side to side and front/back stability must be provided. Cables with turn-buckles provide the lateral stiffness, and struts attached to the roof rack stabilize the fore/aft direction.
The struts are attached to the roof rack by a hinged clamp that is held shut with a wing nut. I'm not happy with this design, as it is possible to snap/rip the glider bag. I have several ideas to change that, but haven't done them yet. The rack end of the strut has an open ended hook that fits into a slot routed into the top of the rack. One cable end loop slips on this hook when inserted, and the other end attaches to a pin in the upright. When the turn buckle is snugged it holds the struct hook firmly in the slot.
Another requirement I had is that I be able to open the hood with the rack attached, to check oil on long trips. All I need to do is loosen the turnbuckles and unhook the lower ends of the cables. The countersunk screws, a slight outward bend in the hinge, and a slight widening at the top provide the necessary clearance.
The rack was made from red oak. As a final check, there was the Load Test:
The hinge pins for the uprights are staggered in height, so one leg will fold over the other. The space below the upper leg provides storage for the cables and hinge attachment screws.