This is right on the money. ^^^^
An Envy knot for instance, which is one of the denser knots you can buy by itself, set into a 26mm opening is going to feel almost like a 28.
Here are two brushes with the same 24 mm Envy knot, set to a mm's difference in free loft, but the Doug Korn has a smaller opening, and the Nathan Clark is right about at a 26.
Two completely different brushes; both just excellent. The one on the right definitely feels like a bigger brush though.
If a guy didn't want to drop that much ($60 ish) into a knot, I would look at a TGN 2 band finest. A similar knot, just a little less dense, and probably a little less soft. Still really good knots though. I have several, and wouldn't hesitate to buy more.
If you want Silvertip, I would again recommend looking at TGN.
@Douglas Carey has one in grade A and has spoken highly of it. It was recommended to him by @Boojum. If either one of them recommends a knot, you can take that straight to the bank.

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