Shopping for resistors

[35L6]

My projects have been mostly low voltage so I haven't paid much attention to voltage limits but this one is high voltage . My PT is Hammond 290TRB . NLV is 295V across each half winding . I wanted to use the full wave bias supply from pg219 of Merlin's power supply book . It has a 100k 1W from the diodes to ground . So I was looking at 500V resistors and noticed a foot note that said sq root of P x R .This gives me 316V . Is this something to worry about or how should I spec this resistor ?

[Helmholtz]

Well, when the resistor drops more than 316V, its 1W rating will be exceeded.
With 500V across the resistor it would dissipate 2.5W.
With your secondary voltage you will need a 2W minimum resistor.

[35L6]

Thanks