From experience I can tell you DO NOT use anything steel to weight down your hop bag, unless you are 100% positive it is stainless! Otherwise the 'I' in IPA will stand for a distinct iron taste. I use marbles for sinking, tie a piece of fishing line to the bag, and learned that dry hopping with a bag in a bucket is exponentially easier than doing it in a carboy as pulling out the bag is a huge PITA. BUT, BUT, this last big ipa I double dry hopped in the carboy has HUGE hop flavor and I would have to say it is from the difficulty of pulling the hop bag back out...in the struggle the hops were completely squeezed of all liquid. As I am just thinking about it, this may be similar to how a hop rocket works.....hmmm.