I have a 800 x 800 cast shower tray to fit in the morning.  I have done lots 
of these but never on my own due to the weight and awkwardness, (my helper 
is on holiday).  As I need to bed it down on 1/2" mortar and lift it into 
position by myself, I was thinking of using two lengths of 1/2" square 
timber about 150mm from the edges and level the mortar to these, put the 
tray on the top (with a few grunts etc.) and pull the timbers out.  Will it 
work and will it have any detriment on the tray support, as technically it 
will not be 'fully' supported it will have two 1/2" channels running front 
to back.  Any other ideas?  The tray is in a corner situation and I have 
easy access to the other two edges.

Cheers

John