I've seen various bodge solutions to this but am interested in how a professional would approach it. I am fitting a bath 90mm too short for the space its going into. I'm looking at boxing out and tiling the gap somehow but i want to do it properly so that water drains into the bath, even after some movement, and also so it looks good. Horizontal tiles flush with the bath lip don't seem a good idea to me: i think they need to overlap the lip and not be level so they drain. This must be a common issue??