silver conducts more efficiently than brass. That would be the first thing I would look at.
Of course, a simple practical solution would be to simply build a hotter coil (assuming you arent using one that is bordering the edges of safety and sanity already)
It's actually copper contacts on the stingray clone, I knew silver was better, but thought the copper body and threading would perform better than the ss nemesis. I actually just did a new coil set up, the original was 26g 5 dual wrap micro coils at .3 ohms and now is 24g 4 dual wrap micro coils at .21, it feels better, but still not a hot vape, and less dense and vapor.
Take the mod apart and clean everything - Twice for luck.
Something is reducing current and the Mod should be hitting just as hard!
Are you running one of the very Few BOTTOM air flow RDA's? If not, the Stingray air slots cannot have an effect on anything.
Cooler Vape and less Vapor is Loss of current flow.
If you knew how to use a multimeter you could find the fault in a few minutes.
I'm using 3 caps 1 is drilled out to I believe 9/64 and the other to 9/64 + 2 small original air holes besides the originals and the other is a cyclops style.
I was reading that the top cap features an atomizer venting system.