Sure, give em a try. The thing about all this stuff is, its pretty easy or at least predictable to say what will happen with something like what you did, mass loading. But anything beyond that- what mix, how much, etc- is pure trial and error. Including the springs.
That's because what all this stuff is doing is controlling vibration. The springs are worth getting if only to learn about vibration control. The number of springs relative to the weight above them determines the resonant frequency of the component/spring system that in turn determines the effect on the sound that you hear. Nobsound springs make it easy to remove one or two springs and hear the difference. Stiffer is more top end less bottom end, softer is more bass less treble, and the sweet spot in between is the best of both worlds plus lower noise and greater dynamics and with less glare and a more natural sound.
You will hear more or less similar effects changing amounts of sand and lead, but compared to how much work and mess the springs are by far the way to go.
The pucks you have, almost certainly better than bolted. Almost anything will probably be better than bolted.
