hi all,just finishing my 1st slate job with clibrated green slate,looks good yet i have 2 tiles with slight lippage the slate was the same size but thicknesses were different by 3 to 4 mm on some tiles,ive heard you guys talking bout using a bolster to removes this but can you also do it on calibrated slate?? lippage is minor but i still would be happier if i could remove it?cheers