My mother has advanced emphysema needs to be on at least a setting of 4 continuous flow to leave the house. I bought 2 large size E tanks that have built-in regulators but they do not fit her homefill system. Does anyone know if I can unscrew the fill port on the E tank and just swap the adapter from one of her smaller tanks so she can use the homefill system to fill these? It would be so wonderfull to have these to use so she can stay out longer.