: Hi Mike,
: I made my cheek plates about 6" wide. But the big thing is where you
: mount them. Make sure you get them back in the cockpit far enough. I found
: out the hard way that mine are to far forward. It really makes a
: difference when it comes to rolling! I think the easiest way to describe
: the location is the widest point in the cockpit.

I would think more in terms of positioning them near the widest point of the paddler, rather than the hull. In a "fishform" shaped hull, the widest point of the hull could be around your knees.

The width will depend somewhat on the way you sit in your boat. If you typically sit with your knees spread apart, the front edge of a wide cheek plate is likely to dig into your thighs. If you paddle with your knees fairly close together, it's less of an issue. I would suggest cheek plates ~4" wide, since all they're there for is to prevent you from slopping around from side to side as you lean, edge and roll. Be sure to leave enough room for 1/4" or more of padding on each side.

BTW, the spaces between the cheek plates and the hull can be very useful. I typically stuff a bailing sponge into one side and make a minicell block to hold signal flares behind the other. If your hull is wide enough, you may even have room to store your bilge pump behind one of the cheek plates.