What I did..
I made every single screw on my -4 the same (8-32) and used reduced 100 degree head titanium screws (Boeing BACB30VF series screw). These screws have same head diameter as a 6-32 screw but an 8-32 shank. I used the same thing for fairings,wingtips,panels,cowling, interior panels, ect. This way, I don't have to keep inventory of several sizes, and the titanium is light and corrosion resistant. I also use reduced diameter stainless skin washers on all the exterior items. Small, light and tidy.