On my classical guitar I never had any trouble with this chord, but with my new electro-acoustic I can't seem to find a way to not hit the high e string with my ring finger (am pressing the 3 above strings down with this finger), turning it into a 6th chord. I guess the fretboard is narrower..

Any advice?
Mute it?

I really don't get what your talking about so, I can't really say.. Sorry.
You are barring across 5 with first finger and barring across 7 (trying to let high e remain fretted on 5?) with your third finger?

This is a pain in the ass chord shape. It just takes time and paying attention when you form the chord structure.

I'm in a similar boat. I used to not be able to play this chord without sounding the high string 2 frets up from where I wanted it. No I've got it to the stage where it's just muted. Which works well enough for my needs, but if you want to sound the full chord, you need to spend time training your fingers.