i do it with all of my 9550's. it's seemingly more susceptable to noise, but using the inductor that ko propo supplies with their fet servos helps that. it also seems sensitive to where in the +ive line you tap into.
i have not had any adverse effects over the course of 10 months running weekly to twice a week. while the servo motor is going to wear faster with higher voltage applied, i am satisfied with what i've already acheived in the 10 months. i would be surprised if i do burn one up.
mind you, i am not proposing this as a solution to spending the big $. the 9550 is already top of the line. i love it for what it is, but i have struggled with the semi-slow transit time that it has at 6.0v. with cars getting less and less tollerant of larger electronics, the 9550 is a great weapon to have. i don't think it would be my first choice if i had to run it on 6 volts, though.
- chris