Lexan headlight covers are formed to fit the shape of the headlight scoops on the Velo Rossa™. Price is for a pair. 

These headlight covers have good shape and optical clarity for hand fabrication.  

I supply them with a rough trim, and they are probably a bit larger than what you need. This is so you can fit them to a variety of GTO kits (Eagle, Alpha, Blue Ray Rhino, and Velo Rossa™; all of which may differ slightly. McBurnie kits may require a little hot work to fit perfectly.) To finish trim, you'll want to tape them to the car and mark where you want the edge. 

I'd suggest you then use wide blue masking tape to completely cover the top side, and retrim upside down, in a bandsaw with a medium or fine tooth, narrow blade. Take it slow, particularly going around the tighter radii.

Then you can do fine-fitting using a disk sander or belt sander, working parallel with the edge, and then smooth by hand with finer sandpaper. It is possible to "flame" the edges with a propane torch, but you'd want to practice on some of your trim-off!

When you are ready to mount on the car, my preference is to use aluminum brackets, which you can fab from hardware store 1/2" x 1/8" aluminum strips. Mark them off every inch, with two adjacent segments to eventually be bent to form one bracket. 

Before you cut the strip, however, drill your holes. One end of each bracket will get a thru-hole to allow for attachment with a machine-thread screw and nut through the fiberglass headlight scoop. 

The other end can be drilled slightly smaller than the screws you'll use to attach the headlight cover to the bracket. You can tap the screw holes to match the screws. 

For these screws I use an Allen-head machine screws, either zinc-plated or stainless, 10-24, or 10-32. A plated or stainless washer underneath will help distribute the loading and help prevent cracking of the plastic. You can also use a plastic or rubber washer underneath the metal washer.

Once your holes are drilled and tapped, you can cut the brackets apart. Round the corners on the free end of the strip, bend the angle (see below), and cut the bracket away from the bar. Repeat eight times.  Then dress the opposite corners of each bracket.

With the headlight removed from the bonnet or fender, tape the headlight cover in-place. Working through the headlight hole, you can position your brackets (I use four on each side, two bent slightly less than 90 and two slightly more) and tape in-place. 

Remove the headlight cover and drill holes in the walls of the headlight scoops. Fasten the brackets with screws and nuts (and sealant if you like) before re-positioning the headlight cover. 

Mark the holes to be drilled in the headlight cover. When you drill it, it's best to have it upside down and against a firm surface like a piece of wood. 

Many folks use special drill bits to help prevent cracking the plastic. You can actually modify a regular bit by gently grinding a small radius on the shoulders of the cutting point. This helps prevent the bit from catching on the last little bit of plastic as it penetrates, and it will melt its way through the final portion. A drill press will help prevent cracking due to wandering of the drilling angle.

Remember when drilling plastic, start small, sneak up on the size you want, and you should end up about 10% bigger than the size of the fastener. 

Once you are done you can mount the headlight cover. However, I do two more things that you might like to try:

1. You can spray paint the headlight scoop silver. This is just a  neat look, but it also helps disperse a little light to the sides of the car, which can be helpful at night when turning.

2. You can mask off, scuff, and paint a silver band inside your headlight covers. This has the visual effect of a trim ring, and it also helps over sealant if you want to seal your headlight covers to the body. If you do, clear RTV silicone will work, and you can use silicone spray as a release agent applied to the body so you can remove the headlight covers later on, if needed.

You might also think about drilling a very small drain hole at the lowest point of the headlight scoop to drain any water that might sneak past your seals.

When you are done with all that, you can re-install the headlights.