Thanks for those videos. I've tried the method of setting a subtool to subtractive, merging it into the other subtool and then dynameshing but it's appending it instead of removing it like in my original screenshots. I've done exactly as he does and once merged the cylinder is the white polygroup that it should be but it…
Yep, that was my problem at one point, I needed to make the cylinder or shape I wanted booleaned/cut out/subtracted LARGER in order for Zbrush to make the calculations. Sure it might mess up what you've already got because of the larger size of the cylinder, but that's the good thing about Zbrush, you can fix things pretty…