But your test is only going to show what they are doing at rest. or what they aren't doing at rest. I think when they do the most is when the string has been released and then how much or how many times would the string try to bounce back and forth before coming to rest. That's what I'd guess the suppressor help the most, at stopping the string from bouncing back and forth!
So just plucking the string with and without suppressors and then with and without leaches won't show me much because the although the string does rest on the suppressor, the string is in heavy contact, or has more pressure on them while in motion! So it seems to me that the suppressors job is to bring the string back to rest quicker!
I can guess what your test will show!!