If you can move the rollers in you should be able to fit a 16 on it.
Actually, the rollers move out
when you go from a 14 to a 16 on a trailer. 3" out each, to be precise.
Most trailer manufacturers that I'm familiar with only made one size cat trailer. They were designed to be adjusted to the boat. Usually the rollers are bolted on crossbars which in turn are usually bolted to the trailer frame using U-bolts. SImply reposition the crossbars forward or backward a little so that the rollers are directly under the 16's pylons and you're done.
If you do that, there will be significantly more weight on the front trailer crossbar than the rear, since the boat's center of gravity is forward of the shroud attachments (when the rig is off).
Front trailer crossbar needs to be ~ 1 ft forward of the front pylon.
Most small trailers have a 1000 lb capacity, so the weight shouldn't be a problem.