I generally bond them in after joining the deck to the hull and bond them to both the deck and the hull (un-like nick's system). I find it pretty easy to do and to make very strong.

checking one of my drawings, the cockpit is 30 and 3/4 inches long, the hip braces are 10 inches long (wide) by about 7 inches tall. 8 inches wide is generally enough. they start 6 inches from the back of the cockpit (inside the combing) and run to 16 inches. Make them more or less vertical but sloping them out is OK too. make sure they are wide enough for your hips with room to spare for padding!