This is great! I also like to remove the string bucket (I have a lathe so it is a little easier). I can’t say that I feel a noticeable difference afterward removing the bucket alone but I sure do like being able to dump all the string in there quickly, and having access inside for fine tuning. I have not tried your o-ring idea yet but it sure seems like a worthwhile mod to me.
Another thing I have used to add weight in a small top is to add silicone in the bottom third. Just dump it in there, level it and let it cure. This mod may not work with this top however; I heard even adding the weight of a metal tip confuses the spin axis (totally not the correct scientific term but yeah) and the thing just spins wild.