I have a large mirror 62” x 36” x 1/4” that is secured to the exterior bathroom wall using a j-channel at the bottom (secured into studs I believe) and tan mastic behind the mirror itself.  At the top of the mirror is another j-channel but it is just glued in place.

From my other thread I am concerned about the paint adhesion so I want to add supplemental clips.

One option is to install clips on the side of the mirror, about 7 inches from the top and bottom on each side for a total of 4 clips using plastic anchors.  In theses areas the drywall was skimmed because the old mirror removal tore out the paper.

The second option is to install two clips at the top and have the clips overlap the decorative j-channel and screwing those each into stud.  Luckily the stud placement allows me to get the clips 10 inches in from one corner of the mirror and 8 inches in from the other side.  Not perfect spacing but unless you really pay attention I think it would be hard to notice because of the bathroom layout.  

The problem with option two is that there is a gap between the clip and the wall so I’d need a spacer.  Additionally I’m wondering about dissimilar metal corrosion since the j-channel appears to be aluminum, the clips chrome, and the longer wood screw I would need to make this work zinc.  The only thing I could think is to use a 1mm plastic space to separate the clip and j-channel.  I do trust stud anchoring way more than plastic drywall anchors

Here’s a pic of the clip at the top to show the gap.

https://imgur.com/a/UqspLbZ

Here’s a pic of one installed at the side

https://i.imgur.com/uS9b5Gl.png

Why do you guys think?

Hit the studs they aren’t going anywhere. So long as the bottom is solid even one on the top that hits a stud should hold it in place. There are other styles of hollow wall anchors. Beside the plastic ones. One other option is to add an oak or other hardwood (bacote) board along the full length of the top with it router cut to overlap the top and screwed to the studs.

The only wall anchors that will fit on the side are these shoulder less anchors.

So you’d mount at top is sounds like it?

Any concerns about dissimilar metal corrosion ?

I kind of like the idea of making a custom routered top wood trim board in an exotic hardwood. Bacote, Paduk, zebra wood, Cocobolo, ebony, whatever matches your color choices or accents them. With wood the type screws don’t matter. You could use stainless but they are soft and tend to break if you don’t have a pilot hole.
https://www.homedepot.com/p/Everbilt-3-16-in-x-3-in-Zinc-Plated-Steel-Phillips-Mushroom-Head-Toggle-Bolt-Anchors-15-Pack-803922/204273381 to use theses you drill a hole, have the retaining clip that holds the mirror on the bolt before pushing the back through the hole the wings under spring tension pop out to the sides and you hold pressure on them as you tighten it.

Get EZ Anchors.

I have literally hung a 65" TV with nothing but four EZ Anchors. It was perfectly secure.

For the top or side?  The only anchors that will fit on the side are the slim plastic shoulder less anchors

If you're worried about dissimilar metal corrosion, use stainless or brass screws.

I’m more worried about the chrome clip and aluminum channel corroding.  But I think a 1mm plastic spacer would mitigate this

I used these clips on a 48' X 36" mirror;

My glass guy provided these.

Yeah but once the mirror is glued to the wall I can use those

Why do they need to be shoulder less exactly?

For what it's worth EZ Anchors are shoulder less. They do not protrude from the wall, at all.

Use a flexible glue or silicone sealer.  If you use a rigid glue, it may make waves in your mirror.

That is why we install laser mirrors with silicone.  

I just installed two mirrors yesterday.  They came with thin aluminum French cleats that were already glued to the rear of the mirrors.  These were toward the top, and rubber titties were provided to stabilize the base. Each mirror was around 36" x 24".

Another thing to note is that this is the second time I remodeled this bathroom.  Take this into consideration with your install.