I know that there is a real danger of hypersensitivity being caused by a cross reaction resulting from the exposure to components of Snake venom from sources other than the animal in question. For instance you may never have had any contact with C. Atrox, but you have spent years working with C. Contortrix. There is a very real danger that the diamond backs bite could trigger and allergic reaction due to the components that it’s venom shares with the copper heads venom, that you have been exposed to. Knowing little to nothing about H. Gigas venom it is pure speculation for me, but I would think that it’s more than likely the venom that they have shares several of its many components with other venoms that a person may have been exposed to. So I think it is within the realm of possibility that given the right set of circumstances if a person did somehow manage to get FWC venom in to their body, that you could have an allergic reaction even if you had never been exposed gigas venom in the past. That being said, the likelihood of someone suffering a severe allergic response to a bite from this species is so unlikely that it barley even warrants mentioning.