TheScullster wrote:

There seem to be various types on the market, some of which look well waffey
to me!

It's not the boxes that give out but the plasterboard. Most seem to have
the same size sideflaps so little to choose there in terms of load
spreading. To my mind they'd be better if they had extra flaps top and
bottom on the double boxes as they're nearly always going to be socket
boxes.

Having said that, I fitted a double socket in an existing plasterboard
wall the other day using one and was surprised at how solid it felt.

If it was me, I'd simply set a 35mm metal back box into the existing
wall so that it'll sit flush with (or slightly behind) the front face of
the plasterboard when it's fitted.

--
Scott

Where are we going and why am I in this handbasket?