There's a difference between flattering slimness and unflattering slimness - the former is not for everyone, unfortunately, as it requires the owner's body to be nicely slim as well. You'll want to get a tailor to let the waist and lower chest (around the bottom half of the lapel) out a little or lose a few kilos, since people will see the suit pulling unattractively at the seams. The sleeve width is fine. Make sure to get the sleeve length right.
8/7/14 at 1:00pm