I don't believe there is much added benefit to mounting an
AIS B antenna higher that 14' to 18' off the
water: a handheld VHF has more than twice the
power and is limited to less than a dozen miles
with line of sight. Vessels with short AIS antennas mounted on the pushpit report receiving AIS positions at 26 miles, or almost an hour warning in a worst-case head-on scenario.
Your
GPS antenna should be mounted as low as possible with a relatively clear sky view on a sailboat. The
cabin roof is the best bet. The motion of the antenna when mounted higher causes problems. Note that it should have a clear view down to the horizon, as more widely separated satellites yield better triangulation. It you also mount a
satellite radio antenna, it needs a clear view at low angles too.
I, too am pleased that a whip is a good
ssb antenna, even though I have an insulated backstay. The verticality issue is of less relevance with an
SSB, because it is not line of site, strictly speaking.
I have an omni-directional
wifi antenna with exceptional range, but that's still no more than 5 miles. The only reason to raise it would be to see over another boat or over a breakwater. The added height only exacerbates the problem of powering the antenna. Mine is on the same (fiberglass) pole as my AIS antenna.