[Amps] boost transformer

[Wayne Newport]

hi all, I just wanted an opinion I have a  DC power supply but I need 3400V for a project.I was looking at using a boost transformer. Antek have a toroid @ 34V 8 amps. Can the 34V secondary be put in series with the 240V primary of my main transformer to boost the secondary HV. I calculate that when rectified and filtered the 34V should get me about 420V extra DC voltage. Are there any pitfalls to using this boost transformer method
regards Wayne VK4WTN