I'm with lonerider on this one. Don't be afraid of a longer board. Get one that suits your weight (or target weight). 159 is a little short for a 210 pound guy!
There's nothing that magically changes between a 159 and a 163. It's a 4 cm longer board... That's a 2.5% difference! It's not like it's a foot longer.
There's a limiting factor at either end of the spectrum. Too short and it'll get chattery and wash out at higher speeds, too long and it'll be harder to spin and tougher to toss around in the trees.
Alpine boarders ride upwards of 180-185 cm boards regularly, and those guys can carve pretty hard turns, so there's nothing that says going up in size a little is going to make it impossible to turn.
Edit: I started on a 153 when I was under 150 pounds. I'm about 165 now and have been on a few 159's, just ordered my new board in a 160 but it's got a much longer effective edge than a traditional board, so it should ride more like a 165-170 while carving.