Caterham will remove bigheads if fitted, and being prepared for IVA, actually that's not 100% true, they will over bond them, leaving them unrecoverable. Its not the bighead or the tie wrap fixing, it's the minor (and I mean minor) lateral movement that caused IVA problems. If you want bigheads for IVA get the version with the male thread, and bolt the wing to the stays, removable and bonded, but IVA compliant that waits to be seen, but at least Caterham will present with them fitted.