Hi, Barthlomews and nice to see one more catamarans fun!
Coming back to Your qtns, IMHO:
1) Are the premium SA cats on par with the top european brands?
In general the answer is "yes". The only question is to chose/find right
boat matching Your sailing ideas as much as possible.
2)Are the pretty Euro cats
seaworthy for long term
offshore cruising?
Not all and every of them. Keeping in mind particularly OFFSHORE sailing
and permanently year by year lowering building quality by all most known
production boat builders.
3) What length of vessel should I ideally be looking at for 6 persons.
Depending of how long is Your long term.
For 3 of You 40-ft might be fine, if Your friends will share all time with You,
then bigger one seems to be better. We are always 5-6 onboard and
from, time to time our 50-ft appears to be small!
4)If I opt for a Euro boat, is it a major hassle
buying a boat remotely?
Just "buying" is simple.
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Having sailed various cats during last 9 years I personally see a "long term
live-aboard offshore capable cat" as a purpose designed boat built in quality materials by reliable yard. Regular visiting to see how the boat is built is essential as well.
Good luck!