I've been using Topeak trunk bag, but with winter, I'd like the added flexibility of panniers. I have a grocery pannier (Avenir), but had heelstrike problems, and had to drill new holes, and move one of the hooks about an inch. Now I'm fine with it. Can I use this information to pick more traditional panniers I won't have problem with? Is the grocery pannier design more conducive to heelstrike? Less? Can one draw broad conclusions like that? I haven't seen much selection at any of my LBSs, so I anticipate purchases being online. Can't try them out first.