Sorry, don't know where i got 67kg from, its actually close to 40kg.
I apologise for the overestimation.
In any case, maybe I should have been more descriptive, if you want to fit a bracket that doesn't move in any direction, then maybe using toggles would be sufficient if the mounting bracket plate was large enough, but i'd never do it.
If you fit an adjustable bracket, like the ones that swing away from the wall and up and down etc, then they need to be anchored into a solid wall IN MY OPINION. Just like ESS_THREE could probably run his porsche on bald tyres and it would probably be fine in most conditions, but why take the risk?
My Plasma cost me a lot of money and i'd not hang it on plasterboard of any thickness. When our company fit the wall mounted data cabinets as described earlier, we first screw a larger sheet of MDF to the wall then screw the cab onto that, because if it falls off then someones safety could be put at risk, and thats not something we would take a chance on.
If I wanted to fit a plasma to the wall and all I had was galv studding, i'd locate the studs either side of the site for fitting the screen and then cut the board out between the 2 verticals, then i'd fabricate a stud framework inside the cavity out of 3x2 sawn timber, anchored firmly to the floor and ceiling joists above. Then i'd fit some convoluted conduit into the wall from the screen position to the ground so that the cables can be run inside the wall but still easily removed.
Then replace the piece of cut out plasterboard with a new piece and get the joint skimmed. Mount the plasma bracket on the new studwork with some 2x10 roundhead screws and penny washers.
This is a longer process and more costly, but its also a lot more professional and resilient than screwing the screen to what is basically chalk and paper.
Now would you want your plasma screen falling off the wall and onto your child?