As mentioned you shouldn't use a tube in a tubeless tyre as the friction between the tube and the tyre can cause a lot of heat leading to premature failure of one or both, and can be catastrophic.
Imagine the inner tube blowing at 70mph and suddenly throwing the balance of the wheel on one corner out massively even worse if it's a steering wheel
Have to say that is one of the worst things i could imagine having a blow out at 60 mph +. Suddenly losing control