As long as this group as been around, I’m surprised they don’t use suits made of lighter, thinner material.
You don’t have to encase yourself inside a walking hot box.
That’s not even healthy.
Maybe most participants use homemade suits, and don’t know what costume designers would know.
Design for ventilation, flexibility and ease of removing.
In reference to the group itself, I think it’s sort of strange, and not something I’d be remotely interested in doing.
All the suits are custom made, and many have built in fans or even liquid cooling. Still, I don’t think I would last 5 minutes in one of those things during the summer.