Only Tom has Tom's meshes for export. He's picky like that
How FBs are made:
1. Decide order of file appearance.
2. Each file gets 196 bytes worth of pre-header data; beginning with the full file path from root (i.e. actors/1001.igb
; the file type and length -- see any FB in hex editor for examples).
3. Each resulting file is C&Ped in a binary merge (best done via hex editing) in the order you've decided on. The order doesn't matter at all, though the game uses the principle of LEVELS->WEAPON MODELS->SKELETONS->CHARACTER MODELS->HUD_HEADS->ICONS->EFFECTS->TEXTURES FOR EFFECTS->ENTITIES->FIGHTSTYLES.
4. Save end result file as FB.
I can't tell you about the parameters you have to set in the 196-byte header though, as I only rip the files apart, hadn't had to build them yet.