Rental-Friendly Mounting Advice?

[CLuz]

So I’ve recently moved from one apartment to a larger one within the same complex. We’d lived in the old unit for four years and had hung some shelves and things after being told when we originally moved in that anything that made a hole smaller than a quarter would be ok as long as we filled the hole and re-matched the wall texture upon move-put. Anything bigger would constitute significant damage that would require specialized repairs (basically that’s the point at where they’d start charging). They even offered a small surcharge to have the company maintenance team install tv mounts for residents who felt they couldn’t confidently do it themselves. 
In anticipation of the move, I purchased all the things to put together this IKEA tile mirror turned large wall mirror (link at bottom). Not exactly this big (4 tiles across & 5 down), but I want it mounted up on the wall and not leaning against it, and I thought I had it all worked out how to do “rental friendly” in my head:

I have multiple pre-cut sheets (24x48” 5mm) of underlayment plywood (I can’t cut larger sheets down at home and don’t have a huge car so I thought this would’ve worked fine for my plan). I was going to glue down the spaced-out trim pieces, paint it all black, then mount each piece to the wall, abutting one another, with either two or four 2 1/2” #8 wood screws through each individual panel into the studs. (I realize that many screws may be overkill but I’m not super experienced and wanted to avoid waking up to 20 mirror tiles all shattering on the floor or something). I then planned to use those heavy duty command strips to affix each mirror tile in its spot within the wood frame (this seemed most convenient for then getting the tiles back off to pack up & being able to take the frame down whenever we move again. Each mirror tile isn’t really heavy and I just spend a bit more and double up on strips per tile, so I’m not concerned with individual mirrors falling off). 
The issue is that we’ve now learned they’ve since quietly changed policies and anything “standard screw size” or larger is not allowed. We can use tacks, picture nails, and command strips. I’m not worried necessarily about fixing the actual mirrors to the walls cause I know I can do all that with command strips. But the frame & trim between each tile is more of an issue. 
The way I see it, these are the best options:

1. Eat the cost of all the plywood and trim I already bought. Go buy longer uncut strips from the mounding section and try to borrow a car to get it home, then cut them by hand and piece the whole frame together with, idk, wood glue and picture nails? Then attach the relatively lightweight frame straight to the wall with no back piece and put each mirror tile in individually, using command strips to stick them directly onto the wall. Kind of a “floating” situation. But I’m worried this will end up looking kind flimsy and have no margin for error because I’ll have to perfectly hide the light wall instead of having a black background to hide some gaps here & there. 
—OR—

2. Use the biggest picture nails I can find and use those instead of the screws for the same initial concept still using the plywood painted black for the base of the whole frame. I’ll have to use more nails, but the holes can be filled so easily that more holes doesn’t necessarily bother me. But idk at which point it’s still just like an absurd proposition? 

The whole piece overall is probably around 200 pounds max. The mirrors themselves were the highest cost of the whole thing, and I really want to utilize them and I can’t return them anymore. So I’m just trying to figure out the best way. 
 

For visual reference, here’s an Example of the mirror

Any advice? Thanks in advance! 

[wtnhighlander]

@CLuz, I can't say much about the wall damage issue, because you are going to need some reasonable screws or a bucket full of nails to hang all that. Best bet is to eat the cost of patch and paint when you move.

Aside from that, I hung a similarly-sized mirror thing, three pieces in steel framing that fir together to form a large, arch-top window-like thing. Weighs a couple hundred pounds. I assembled the pieces onto a 3/4" plywood backer, cut to match the shape, and painted to match the bronze colored steel framework. Before assembly, I cut a 6" wide slot across the backer, about 3/4 of its width and located maybe 3/5 of the backer's height from the bottom. the upper edge of the slot was cut at a 45* angle through the thickness, and the off-cut was shortened maybe 6" in length. The result was a 'French Cleat', with the off-cut screwd into the wall studs. The cleat being shorter than the slot in the backer allows for side-to-side adjustment. Install the cleat level, then hanging that heavy mirror is a piece of cake.

[Coop]

@wtnhighlander‘s has great advise with the French cleat. I would go with your original idea of making it in one piece. 

I have used all kinds of wall anchors in my life, from nylon tap ins to standard toggle bolts and found out about these when I helped my daughter move. The hole needed is very minimal and as it has it’s own built in plastic washer head, it can be patched easily. Each toggle will support over 100 lbs. so 3 would be required in your case. 

https://www.homedepot.com/p/FLIPTOGGLE-1-4-in-x-2-1-2-in-Toggle-Bolt-10-Pack-425R/206347693

Also, if you can use the French cleat idea or even going with individual hooks/hangers, these screws are great for attaching them to studs.

https://www.homedepot.com/p/GRK-Fasteners-8-x-2-3-4-in-Star-Drive-Low-Profile-Washer-Head-Cabinet-Screw-100-Piece-per-Pack-113081/203525316