I'm trying to mount a TV, but the only studs are on the outside walls of this niche in my fireplace. Meaning I could build a little wooden box and lag into the narrow face of the studs (the 1.5" thickness, instead of the normal 3.5" thickness).
But I've never lagged into the side of a stud before. Is it strong enough to hold hundreds of pounds? This will be an extension arm mount for a heavy 70" HDTV, so it really needs to be strong.