I've never tried the steel plug in the end of these Victa mowers but have used solid round steel where the handle mounts to the base on vintage alloy base mowers.
With the Victa ,I would usually replace if the tubes are too flat or use 2 bits of wood and hammer the tube round again ,then panel beat the top of the deck so there is a nice channel for the tube and always make sure there is the 2 reinforcement plates ,one under the base and the one on top of the tube.
