I want to buy a Carradice Camper Longflap saddle bag for commuting and light weekend touring. My saddle is a specialized something or other (forgot the model) without bag loops. I know I'll need something to attach the straps too but I'm sure what to get. There is this thing, but will I need some kind of support as well? I can buy this but will I still need the other thing to attach the bag too? It looks like it has a place to attach the straps already intergrated into the frame but I'm not sure. What do you all think?