thinking i want a rear bag, but i dont have room for fenders or rack mounting holes, are there any ways to mount a bag on the seatpost somehow? maybe using something coming out of the rear brake mount for some kind of support instead of a fender? any quick-releasing/velcro/anything other than something that requires tools? and then where do i put my taillight? i really dont want to wear a backpack... and theres a bike i keep at work too just for riding from greenhouse to greenhouse and i want to be able to take the bag of my road bike and pop it on the coaster brake one for work. actually if i can find some quick release fenders it could make my bag choices easier. has to be big enough to fit size 8-9 work boots, shorts, t-shirt, socks, underwear, safety glasses, ball cap, gardening gloves, and a couple sandwiches.
Topeak makes a QR seat post rack that can hold 20lbs. It even has specific bags that clip into it and add in side frames for panniers, and a clip on fender.
http://topeak.com/products/Racks
I have the MTX v-type and ride 5 days a week, 6 miles round trip. I didn't get their specific bag, just got some bungee cords and strap my backpack to it (I leave my uniform and boots at work usually but I haul it occasionally). I have it on during the week, for when I go on post office runs, and then just pop it off for weekend rides. Pics in my pedalroom
The only thing I've noticed is my inner thighs rub the clamping mechanism. It doesn't rub bad or chafe, it's just something I noticed, and eventually I forget about it.