I think we are talking about the same plans. I'm well aware of the safety issue and as you've seen it was mentioned with the plans and the option to overcome it. I think the steps are : to build it and if it seems ok, then to add the isolation transformer, unless some one will come up with a better plan/solution.
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buy one........
We're talking 300V at a serious current. I would not attempt it unless you have plans that include proper isolation, that would require winding a custom transformer.