Let’s talk about thumbs and anchors

[micguy]

I have a thumb rest mounted alongside the B string (5 strings) I anchor my thumb on the side of it when playing the B string, and on top of it/against the B string when playing other strings. I don’t float any further - my basses are 17.5 mm spacing, and…I have ginormous hands, so the reach to the G string is quite comfortable.

Your hand size, how many strings you have, and the string spacing all play a role in what will work for you. If you have a 6 string, 19 mm spacing, and short fingers, you’re gonna need to float your thumb.

 

[Ritter667]

Floating thumb!

 

[pepj]

IMV you need a precise, accurate and articulate fretting hand and then you can anchor the plucking hand thumb alternately on the B and E.
Because your fretting hand is delicate and precise, you don't need much muting beyond anchoring on the B and E.

 

[chris_b]

I used moveable anchor on my 4 string basses and when I found it worked just as well on my 5 string basses I stopped worrying about it and moved on to more important things.