tcad, do me a favor and try it with the original aluminum blind screw (contact head). I just don't see how the brass could be better than the aluminum since aluminum is right at twice the conductivity of brass. (Aluminum about 60% and brass about 30% as good as copper) I would bet it is the rest of what you have done that accounts for the difference.
Edit: clean the aluminum first as aluminum oxide is a poor conductor and that is the main reason we sparky's use Noalox on clean aluminum wire before we terminate it.
That's what I was wondering. Brass and aluminum both tarnish rather easily as well. Part of what appealed to me with the aluminum screw was the big, softly rounded head. It's very easy to clean and polish. (A small, flat head is awkward to rub). However, anything that's #8 x32 thread will fit in there nicely. (any silver machine screws out there?)
As for the stiffer spring. A great thing indeed! My dilemna, the reason (partly) why things are the way they are is as follows. ONCE one knows exactly which batteries are in the mod, THEN one can adjust the throw to a minimum, and incorporate a stiffer spring with better conductivity (based on shear mass). I can't send out mods with 1 mm of throw (because I don't know the battery length or the user's preference). I certainly can offer a stiffer spring in the goody-bag, and folks can custom tailor; but that's just the crux of the dilemna right there. It is a custom setup. So, the spring I use is not the best for voltage; but it is the "best" for everyone's mod firing out of the box. I think I HAVE to continue to do a "one size fits all" for delivery / initial setup, don't I? And then, game on, supremely moddable. And, like I said, I can certainly include the parts necessary for such modding.