How to Hang TV on SIP wall
Just mount it to the wall with short lag bolts. 3/4&quot; OSB is a solid mounting surface unless you soak it with water.
Since you did not specify drywall thickness, you basically want a lag bolt roughly 1/8-1/4&quot; longer than 3/4&quot; plus drywall thickness - so if 1/2&quot; drywall, 1-1/2&quot; lag bolts. Predrill for the core of the lag bolt so it's just cutting threads with its screw, not trying to crush a hole in the wall (as per normal for proper use of lag bolts.)
If mounting a supplementary board to the wall, don't fool around with 1/4-3/8&quot; thick - that's not going to hold (nor help) much at all. Cut out the drywall to the size of your board, use at least 3/4&quot; solid wood or plywood, and attach directly to the OSB with construction adhesive and screws equal to the board + the OSB thickness. Let the adhesive cure before mounting the TV, with lag bolts.
...sent from inside my SIP house.