Definitely agree. Moulded plastic would be one of the better ones. Castings would be ok in some circumstances though the interior cores could be a pain to contr

Definitely agree. Moulded plastic would be one of the better ones. Castings would be ok in some circumstances though the interior cores could be a pain to control, eg: ensuring the sand to create the voids is solid enough not to disentigrate as you try to cast and is not just floating in mid-air.