The biggest drag contributors (besides the tires themselves) on this one iare the blunt back end and the zoomies-in-the-air headers. JMHO, I would do three things:
1. Put 4-into-ones on both sides with the exhaust pointed aft. Both drag and residual thrust will improve. Zoomies are VERY peaky,
www.burnsstainless.com has a great header design service to create the broad powerband needed for LSR without sacrificing the top end.
2. Close out the tail with a proper fairing. Your chute packs face almost vertical anyway, so a tail section/diffuser to fill in the separation will be the biggest drag reduction improvement possible.
3. Leave the wheel track wide. The tires of any lakester are guaranteed to create separated flow, and keeping this away from the body is the best choice. If anything, the rear track should be wider to allow air to cleanly flow between the tires and the body. If this is impractical, look at how Group B and Prototypes use diffuser fences to create vortex flow to fill in the back of the rear tires.