So when your power transistor switches on, where does the power go to? . You should monitor the AC voltage at the drain of the FET and from the rectified output drive an ALC circuit, reducing the drive, to make sure that the output voltage is stabilised at Vrf peak = 2 X Vcc (60V). That way when there is no load, the output voltage is 60V due to low drive. If a load is placed on the circuit, absorbing power from the coil, then the drive increases, to keep the voltage constant.
Frank