I absolutely agree with Wayne. In short Dyneema isn't right for standing rigging. With Vectran you could solve the problem of creep (pre stretching Dyneema is only marketing blabla). But compared to steel of similar diameter I don't like the softness, although I could never measure a difference in speed (I have no jib). Hence this is very to your like. With a jib I would always go with the stiffest material.
Never used PBO, Carbon or Aramid on my boat. None of them like UV and water, hence need sophisticated protection and one would lose the diameter advantage on small boats.

On small cats, rigging drag is more important than weight (cross-section area depends on diameter in square and drives strength and weight, drag depends on diameter only).
The performance difference to 2.5mm steel (for uni) is more in your mind than on the water for a small cat anyway.

Since three or four years I use synthetic ropes (dyneema) to connect the wires to the mast fitting, so that the steel wire never touches the carbon mast. Makes the boat silent as well.
Never had any failure. The boat is exposed the full season to UV and weather.

Cheers,

Klaus