That's an awfully big bag, I would try to get the clothes out of there, and separate the other stuff into two smaller packages. I load my top of rack stuff horizontally, but it's a lot less wide than yours. I don't like it sticking out past the panniers much.
I like the nylon straps with fastex buckles way better than bungies, b/c you can really cinch them down as tight as you need to, bungees don't have enough of a range, and tend to spring loose.
this kind of thing (comes in many sizes):
http://www.rei.com/product/813835/re...release-buckle
Get the front bags and then decide. Look at pictures of other people's loads for ideas. crazyguyonabike has a lot, and the fully loaded touring gallery
http://www.pbase.com/canyonlands/fullyloaded
also - your rear bags look pretty small, like front bags. if you put those in front and get slightly bigger ones in back, you can get more stuff inside the bags and have less strapped outside.
also - consider re-thinking how you pack the tent & pad - they don't have to be rolled/folded up the way they came from the store, there might be a way to pack differently that makes them an easier shape to deal with. keep experimenting, you'll figure out something that works.