Apologies if this question has been answered elsewhere, but before I commit to getting my guitars set-up, I was wondering if anyone has had any trouble using 9–42 tuned down a half-step (I currently use 10's tuned down a half-step). I have a light-touch and have noticed that some players prefer lighter strings (at least on the high-end, like Yngwie).
If it helps, the specific guitars are a Gibson Les Paul Custom and an ESP USA Eclipse.
A more general question is as follows: is there a rule/guideline on how low strings can go? Obviously, tuning 9's down to B would not be optimal, but how low can/should they go?