Another consideration might be how far up the body of the knob the grub screw is. I took one of the knobs off my epic to check sizes and the shaft isn't very long - probably not much more than 1/4 inch.
 
Graeme

jacko..use your ears!!!

Hah! that's ok if you have time to noodle. I have a few different settings that I use during a gig and having markers means I can go to a specific point very quickly.

Graeme - you can see the set screw location on the knob second from right. If you can see a 1/32 hole in a possibly dim light situation then go for it. (I know I couldn't - I can't see 1/16 brass dots on the side of a fingerboard!) There isn't much of a collar left on the top of these knobs though so you'd need to be careful. I don't do very much adjusting on the fly, but if I did I would need to consider something more substantial and high contrast like a notch of some kind.
 
Or LED's....LOL!
 
As it is a lot of my basses have 1/4 stick-on dots on the side of the neck, including the 2 Alembics that don't have LED's.
 
Will