The TR would definitely fit between the H and the NS. I polished mine and it's very week. AT the stock 800 grit US it's a true medium oil ball. If you want it a little weaker try first 2000 Abralon, then try 4000 Abralon
The Buzz would fit, if you can find one.
A polished, or a 4000 Abralon Buzz Attack might also fit there.
Very surprised you need another ball between the NS and the BB.
Is the NS polished or drilled weakly? or
been used enough to need an oil extraction?
Although they last a long time, they still absorb oil and do need it occasionally.
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"None are so blind as those who will not see."