I did some picture editing with my limited capabilities, but maybe it gives you an idea how it may look like this way:
Upper edge of side cover matches the form of the seat and is supported by fat black line with fine white stripes, same or similar as you already have it on the tank 😉
These lines hit upper mount of rear shocks and flow onto rear fender.
Front side of side cover ends in a straight line in parallel with the frame tube. As known from LTDs/CSRs.
The pic with the yellow lines features parallel lines. Base line is lower edge of the tank and repeated at lower edge of side cover.
Have fun and go your own way,