Hello @Goodlife, 
Thanks for sharing your post about your movement challenge. At this time, Creators of Group Challenges may invite up to 24 athletes that follow them on Strava. We cannot modify the number of participants, but you can create multiple elevation Group Challenges of 24 participants each. Please note that group Challenges can be created by subscribers, including athletes with a free trial subscription. All other athletes will get three free challenges to create or join. 

UPDATE ON GROUP CHALLENGES: We are pleased to announce that creators of Group Challenges can now invite up to 199 athletes that follow them on Strava. In order for an athlete to join the challenge, they must be a subscriber, have a free subscription trial, or have free challenges left. Creators can also allow other athletes in the challenge to invite athletes who follow them. From the challenge details screen, tap the three ellipses [...] in the top right to open the challenge settings, and then enable the toggle that reads “Allow Participants to Invite Others”. For more info on Group Challenges, check out this page. 

UPDATE ON GROUP CHALLENGES: Starting in August 2024, only Strava subscribers or users with a free trial will be able to create a group challenge, find out more here.