Hi and welcome to the Breeze..

I'm thinking something about 10' long and preferably about 30" wide.. As far as Naish goes I'd recommend the 9'5" or 10' Mana.. or the 10'6".5 and 10'10" Nalu.. btw they do the 9'5" Mana both of the Nalu's in a beautiful ladies 'Alana' paint job.
I'm sure there are many other brands that have boards in that size range.. Demo, demo, demo.. One good thing about the Naish (and a few other brands) is the good handle because these are big boards to carry and a good handle helps heaps.
Let us know what you end up with.
DJ