Hi Alan,
The trays fitted to all our boats were around the 100 mm depth overall so probably 85 mm water catchment, which was never a problem with either the automatic sump systems or the gulper type ones, as long as you turn it on first
Height was always a problem with shower enclosures, we used to sink our trays down as low as possible, 18 mm ply on the baseplate stiffeners always worked for us.
Our shower doors / enclosures were 1850 mm high domestic products, so you may be able to use them.
If they still manufacture them they were from Plumb Centre, their website is down so can't help further.
Cheers
Roger