13 normally, used to wave around a 16 but went down to 14 and then down again to 13, was skimming with a 12 inch carbon mt Saturday. Can’t see a problem dropping down to smaller sizes for speed and metres done, doesn’t make much difference? Standard is 13 for skimming (nela Carbon) and 13 for render (mt Carbon) Saturday skimming in a very old building in Exeter , plenty of small walls and rolled ceilings and little bits so 12 inch mt Carbon didn’t make a difference, smaller trowel more pressure from the arm per inch of trowel? Nice and flat. Don’t see how it’s possible to scratch on and trowel up with a medi though? Sounds all wrong to me, if I tried that myself it would be full of ripples stripes and lines.