How big do you consider a larger tile ?
CTF3 is a polymer modified cement based adhesive for fixing ceramic wall and floor tiles, ceramic mosaics, quarry tiles, natural stone, terrazzo and brick slips to any standard substrat\backing, ie, concrete/brick/block walling, cement:sand rendering, gypsum plaster, plasterboard, fibre cement sheets, cement:sand screeds, ceramic/quarry tile/terrazzo/hard natural stone, vinyl tiles/sheet, mastic asphalt.
Where as a single part flexi is designed for fixing tiles more along the lines of fully vitirfied and porcelain tiles to low porosity backgrounds/bases.
Suitable for use on concrete/brick/block walling, cement:sand rendering, and also, plaster, plasterboard, cement sheets, tile backer boards, concrete bases, cement:sand screeds, plywood overlay, ceramic/quarry tile/terrazzo/hard natural stone, vinyl tiles/sheet bases, mastic asphalt.
In my view for anything other than fully vitirfied and porcelain tiles on a standard porosity background I would use CTF3, but if I was fixing porcelain I'd go for SPF.
