First Person Model mod body isn't visible when wearing a barrel from The Box Trot mod

(with F1)

Mod Link: https://modrinth.com/mod/the-box-trot
ModLoader: Quilt 0.17.6
The Box Trot: 1.4
FirstPersonModel: 2.2.0

As this is mod conflict issue I'm linking issue in another mod's GitHub issue so you will be able to talk about this issue:
CammiePone/The-Box-Trot#8

I mean, looking at the mod, what the hell should be visible?

Just player body while player is wearing a barrel. Otherwise this just looks weird without a body. Legs and arms floating in the air, eh.
(UPD: Would be cool to see "insides" of the barrel instead of simple on-screen overlay but I think it would be much harder to implement)

I mean, in 3rd person the barrel doesn't rotate, so the entire thing doesn't really apply(you logically shouldn't be able to look down, let alone that the body fits into there). So I don't think there is anything to do here?

Hm, okay. Then... Do you think it is possible to add additional model over player's head and make it compatible with FPM? Or maybe there's an API to do that. If no - what would you recommend to use to render it so it won't conflict with FPM?

See my answer on the other issue.