I cant imagine chipboard taking 50kg on 2 point fixings. The wood strip
under the cupboard is a good way to reinforce them, so is a wood strip
in side the cupboard across the top back.

Any L bracket will work upside down, but baer in mind all the weight on
the shelf is then hanging on a few fixing screws to the bracket, rather
than the wood sitting on the bracket. Think washers if youre putting
weight on it.


NT