If you are bringing enough stuff that you need a frame for your day hikes, then I would just cinch down your main bag.

But... why do you need so much stuff for a day hike? I use one of those rope backpacks that people give away for free (http://www.nbtopgear.com/products/Drawing-Rope-Backpack-885986.html) as a stuff sack and use that on dayhikes. I carry a first aid kit with an emergency blanket, some food and water, a jacket, and maybe my steripen. I have a buddy who has one of the backpacks where the lid comes off and turns into a fanny pack. His backpack weighs quite a bit more than my backpack plus rope sack thing.