I've made a few trips to the hardware store and other errands over the years, using a backpack on my bike (years ago, when it was my only transportation, I hauled a small amount of groceries in a backpack and just made multiple trips) but this is the first trip I've made since I started trying to turn this mountain bike into a cargo bike. I've got the rear rack I talked about in that post, some basic secondhand fabric panniers secured with straps and zip-ties, and a milk crate from a consignment shop. I went for a pretty light grocery run for the first trip, just two totes of frozen stuff, and it rode just fine on the way home.
Thanks for all your advice! I think I'm going to upgrade to bucket panniers at some point soon, but I'm glad I can at least start using it like I'd planned.
That's good to know, and not something I'd thought about but it makes sense how it could cause damage. I definitely need to get a better bike lock or at least a chain - I lost the key to mine and have been using a padlock with a really long shackle, which works on some bike racks and not well on others. Once I've got that, I can probably just put my bike behind that rack and keep from torquing the wheel. Thanks!