Sorry,,, another question....

I understand that the stone resin shower trays are very heavy. The position
of where I want my shower will mean that I need to drill holes through the
joists (estimated around 3 of them) to get the waste pipe through.

Will the drilled joists with what I believe to be 1.5 inch plumbing be
strong enough to support the tray?

Also, from Googling I understand that I need to mount the tray on a mortar
base. What I thought I would do is replace the current MDF floor boards with
a suitable hard wood that I can tile on top of.

I presume then I just put my mortar mix on top of my new boards and set the
resin tray into that.

My question is do I just put a flat layer of mortar on the floor or at
strategic points?

Will the mortar make the shower tray higher than the tiles?

I presume I just scrape away the excess around the outside edge of the tray
to make a neat finish?

Sorry for the beginners questions but I know nothing about this at all! I'm
determined to learn and do this myself rather than get a plumber in - famous
last words!

CM.