Oh! Sorry about that, I did check all the kinds listed at https://github.com/nostr-protocol/nips/tree/master but it's not listed there so assumed it to be OK. This is still under development so no stress to change it 🙏
I'm currently using the following custom kinds:
MeetupCommunity = 1037,
MeetupFollowsList = 10037,
MeetupCommunityMeta = 30037,
MeetupEvent = 1073,
MeetupEventMeta = 30073,
MeetupEventRSVP = 30038
I'll change the RSVP to something else and 30073 will be changing to 31923 to be in line with nip52