I had some openings into the cockpit from the front wheel wells that needed to be closed; otherwise a dust or salt storm would occur at speed. I cut out templates from light cardboard and transferred those to 1/8" plastic sheet. This stuff is polyethylene, used on sprint cars for body panels, etc. It is waterproof, resists rocks, is available in may colors, and is cheap- about $2 a foot in rolls.
I found that aviation tin snips were good tools to cut it and a heat gun allowed it to be formed a little. It drills easily and self-tapping screws make it easy to remove when necessary. I used some yellow plastic to match my chassis color and some black to match my body gelcoat.
It's a little hard to see what's what in this picture but since the front right brake disk is visible it may make sense.
Regards, Neil Tucson, AZ