So I just started playing with a fret and spike at fret 2, and the fifth string is ridiculously loud, and there is a resonance coupling with the third string. I’m still playing with the original set of (light gauge) strings.
I’m wondering if I switching to a higher gauge set of strings would help. Or if is there some other remedy that would dampen the drone and reduce the coupling.
Hmmm, your banjo is probably too in tune 
Man, I honestly don’t know what to tell you here. I’m wondering if the 5th string is maybe hitting something, though it doesn’t sound like it since you say it’s really loud.
I thought about trying to de-tune it a bit and see what happens. I’ll give it a go.
I’ve come to the conclusion that my banjo is tuned especially well for the key of A and that leads to the excessive ringing of the 3rd and 5th strings. I tried taping a quarter to the head of the banjo when I have it fretted, and that seems to help cut down on the resonance.
Very cool you figured that out. Good job! I use a head tensiometer now, but I recall before I tuned the head to G# at other’s suggestions. Maybe G# was favored because it didn’t resonate/interfere with common keys.
Maybe drop the head pitch by a half step?
Yeah, I remember Huber telling me some of the “why” the G# is preferred, but essentially it’s to avoid overtones and create some crunch.