Hi ZB

[br]The chord is indeed an easier one, but you are having problems with it. Need to find out why.

Not trying to be a smarty, just rather perpelexed at the problem as you describe it. I have a serious question for you. How on earth is your palm muting 1st E trying to voice open Cmaj?

My hand (glove) size is medium tending small with proportionate fingers.

I just went and got my APX600 trying to replicate what you describe. It has the same width nut, string spacing, fingerboard radius and scale length as your F310. Even with my fingers/hands, my palm is well clear of anywhere even near the edge of the fretboard, quite impossible to indeliberately mute high E voicing that chord. Lots of air between palm and anywhere near the edge of the fretboard. The F310 and APX600 necks even take the stretch out of voicing open Cmaj.

"Can anyone advise how they approach this chord or have mastered it."

I sense your frustration and wish I could offer some simple solution, but Cmaj was a no brainer for me. The only thing I did to "master" it as such, was finesse the order of placement, the pragmatic perpendiculatrity of my tips, for want of a better word, and curl of the fingers to ensure clean fingering, and smooth changes to and from other chords. Most of that came through awareness generally as I was playing songs, and just repetition playing songs focussing on those aspects during the riff progressions.

I can't recall off hand, but did you mention in a much earlier post that you have either arthritis or a hand injury in your fretting hand? If so, do you suspect this is affecting your flexibility or co-ordination?

Reiterating. Voicing open Cmaj, even with smaller hands, your palm should be nowhere even near 1st E.

In the interim, the alternative 3rd fret barre Cmaj voicing sounds pretty good, and is super easy. Even though it's low on the neck, just slightly more awkward switching between it and open forms generally. e.g. C, Am, F, G. Much easier when deploying it to use all barres, which of course don't ring out on acoustic as opens do.

From another angle. Have you had someone have a look at your F310 to ensure the action is OK? Perhaps your nut is cut too high, you need the relief adjusted or you may have damaged one of the frets or one might not be level from the factory. I'd definitely investigate that getting someone else to give it the once over if you aren't comfortable or up to speed with doing so yourself.

Edit P.S. Lisa has it pretty much nailed in her Cmaj lesson. I just rewatched it to check for you. See how her palm is clear and how her fingers lie to finger the chord in the open voice. However hearing it explained from an alternative perspective might illuminate a light bulb moment for you. All of us agree. Keep trying. You'll get it in the end. It just takes longer for some than others.