I am going to be tiling a concrete screed floor soon, but a little nervous about getting the tiles even. fortunately the floor is even, and therefore the only thing that can ruin it is if i bed the tiles to firm, whilst other not so firm. Therefore I was thinking about laying the adhesive and then laying flat say, a spacer in each area where the tile corners will be so that I can bed the tile down, but only ever down as far a the space, resulting in a constant level floor?