My hubby is 6'5'' tall. Since most matresses are 80 inches long, he mostly ends up with his feet hanging out of the bed (since you don't lay your head down at the very beginning of the mattress, right?). So I tried to solve this problem by making the bed 4'' longer than the plans suggested. I added 2'' of foam on each end of the bed, so now its 84'' long and my hubby fits perfectly!
Thanks for the great plans, I had a blast building my own bed!