For 18 knots up I reckon Futura 93l would be best. That's what I use and it's really comfortable even in rough chop and jibes like a charm.
It'll certainly be much faster than your carve 111 and yet easier than an iSonic. If you get one, opt for Wood, not Technora.
JP Super-X 106l, North F8 Ram: 5.8m,