Saw a plumber doing a pan in the Gents at work.
He stood it on 4 or 5 tile spacers (2mm ones probably)
and then siliconed around the base, using enough silicone
that it would have gone right through the 2mm gap and
built up on the other side. I didn't see if he pulled
out the spacers afterwards or cut them off.

--
Andrew Gabriel

Worth bearing in mind - one point worth making is that the silicon is
enough that you don't need to screw the pan down as well.

Rob