[chrisguyw]

I too have wondered why NSR chose UNC4-40 instead of the slightly smaller M2.5 grub screw (M1.3 head)

As has been mentioned above Salvatore raced several classes of steel/scratchbuilt  cars for many years before he began producing plastic cars.
The standard at that time (worldwide, for slotcars) was UNC-40 set/grub screws, and he adopted this size in the NSR line of cars.

Ernies' chassis have been used off and on by many Wing/Eurosport racers......I did a review of his soon to be released 1/32 (home/club) chassis, elsewhere on this forum.

Cheers
Chris Walker