There is a bit of a run down on power output etc here:

http://www.nzwireless.org/postt52.html

As for line of sight... go for broke as long as you dont go over the db levels in the post above.

But i am sure there arent any police around who would give too much of a rats arse....HOWEVER.... if you throw your signal around willy nilly you will block the sprectrum for other users on the NZwireless network!!

Wookie