Good luck with your entry.
I guess everyone that has done an 'ultra' is doing there first at some point, so as an organiser you might have in mind to have a percentage of first timers in the field. Hopefully they will look at broader cycling experience as well, not just if you have completed an event beginning with 'trans'.
I think there were 30 riders for the first event in 2019, and less last year due to the self sufficient element. I imagine they will want to be growing the event to some extent but at the same time they won't want to go too big. Somewhere between 40 and 60 riders on the start line seems feasible to me, no idea though really(?)