TV Mount Question

[upprc04]

I have asked this at AVS forum and haven't got any responses.  I have received a lot of help from these forums, so I thought I would pick your guys' brains.

I am planning to mount a 60" Plasma (88lbs) in a space above my fireplace. I bought a house recently. The last owner had a similar sized TV mounted at the same place. I got this mount: http://www.ebay.com/itm/120885640796?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 (just linking for reference - let me know if it is against forum rules and I'll remove).  There is a mantle around the fireplace that is about 10 inches deep.  There is currently a fake wall (looks to be .75 inch plywood with chalkboard paint or something similar on the front).  I think it was painted black to blend in behind the TV and not be distracting.

I was hoping there was some studs behind the fake wall but I took it off recently and there aren't any. I attached a quick MSPaint sketch of what is there. The black line is the mantle. The red lines are 2x2's that are screwed in to the mantle. Nothing is screwed in to the back wall other than the mantle being attached.  The blue line doesn't exist currently.

It looks like he attached the old mount directly on to the "fake wall" with no studs to screw in to.  Should I expect the plywood to be strong enough or should I add a 2x4 or something horizontal to connect the wall mount/fake wall too (shown by the blue line - which does not currently exist)?

Thanks!

[Mysterioii]

I personally wouldn't hang a piece of expensive electronic equipment weighing close to 100 pounds off of a sheet of plywood when adding some 2x4 bracing should be extremely easy (and inexpensive).  I don't like taking chances like that.

[upprc04]

I didn't really expect the plywood to hold it.  Is adding a 2x4 horizontal like that good or should I try to put a couple in vertical like it would be in a real wall?  Or does it really matter as long as there is a 2x4 to secure the mount to?

[Green Giant]

I would add two 2x4s horizontally to cover the bottom and top row of bolts.  I have my plasma mounted on a similar wall mount, and you will need support for each row of those horizontal slots.

With them horizontal you can tweak the position you want them mounted instead of vertical where you would only be able to mess with the height.

[kahlid74]

I would add two 2x4s horizontally to cover the bottom and top row of bolts.  I have my plasma mounted on a similar wall mount, and you will need support for each row of those horizontal slots.

With them horizontal you can tweak the position you want them mounted instead of vertical where you would only be able to mess with the height.

This, if you're planning to use the current wall you need two horizontal or vertical braces.  In my experience, the key is using hard woods to hold the screws and balancing the load over softwoods.  The Plywood should be able to hold it as long as a hard wood is used to secure the heavy object.