Very open to feedback and ideas. Contact in my bio. Thanks HN!
Though to be honest I have no idea what kind of info is available from Strava, but I feel that the more you can do on your end and the less involvement required by users, the further you could get with a greater number of people. Relying on people coming to you to sign up for yet another social network seems like a lot to ask of people.
People that run equipment rental stores probably have a facebook group or professional association. If you can befriend someone influential in one of those, it might be a good place to get started.