I am trying to make my racing bike work for all my riding without going to two bikes - something I can't fit into the budget right now. My commute is 16.5 miles each way, all on roads. The seatpost rack is attractive because I can take it off for group rides which I like to do when I can. (These can go up to ~60miles.)

I only need to carry lunch and snacks which is at most 3-4 fruit/veggies and ziplock ~4 cup container. I have no illusions of using it for loaded touring. I am right now using a XL messenger bag from my college days when I lived up north. Besides the mess of pulls it is making in my jersey, I would like to dispense with the bag before the Florida summer is here in all its humid glory.

I have the luxury of working in a University with my own office so I can bring the bike into the building with me. Security-wise I think I would be ok; although something to think about.