forgot, so I will toss it in here...when you put down your decking, USE SCREWS!! Most of the home improvement places sell decking for what you are doing that is tongue and groove and makes a nice even floor. And unless you are planning to store old engine blocks up there, you have a stouter attic than my garage with your 2X6's. I have 2X4 on 24 inch centers and my attic doesn't bow or crack with a LOT of stored stuff up there. And I also have an engine hoisting trestle spanning 5 trusses. You should have no problems. Luck, Kizmet