I have an issue with heel strike when I use panniers or saddlebags, to fix it I either have to get a set-way-back rear rack or use a bike with long chainstays, or use a very tapered pannier bag. I've been setting up this Univega Sportour as a commuter bike, but the chainstays are too short and the rack isn't far enough back to use my panniers. I like this rack on this bike so I don't want to swap it out.
Then a couple of days ago I saw a doggie backpack at a local thrift shop for a few dollars, looked at it, decided to pass. Then later I started thinking about it and decided if it was still there yesterday then I'd get the bags, and they were, so I did get them. They measure about 11"-12" long, and each side is about 5" or so tall and 2.5"-3" wide. Not huge, but maybe just enough to throw a shirt or dress pants into for work if I roll them up. I'm thinking I'll re-do the straps somehow to enable the bags to strap to the rack better, currently the straps are set up to go around a dog which is nothing like a rack on a bike.
Also these have a nifty velcro'd tube on top that looks like it will hold a pump very well.
I'll update this as I progress on this project, but I'm in no real hurry. Hopefully they will work, and hopefully I won't have heel strike with them.
Just throwing out a thought to keep your eyes open for alternatives when rigging up a bike for commuting.
Feel free to add your own projects and discoveries to this if you've found a non-cycling product that works for cycling.