I don't think there is a way to totally kill a guyvers' host, wether or not they're boosted. Theres a mental link between the two, so even if you were to shoot them in the head to cause instant death. I think the guyver would be automatically called as the control metal would sense a loss in brain activity/link, even while awaiting in the boost dimension. So when the unit reboosts the dead host, it heals him and ressurrects the host, brings him back to life.
The only way, for sure to kill the host, we all know is to seperate/erase the host data from the control metal and then kill them or to totally destroy/damage the control metal.
So knowing this, i'll be looking for the remover, then after using it on sho, equip myself with the unit and split him in half with a frequency blade.