If I add a single coil sized Humbucker (Seymour Duncan, dual blade) into the bridge position of an otherwise stock pickup equipped Strat (Fender SCs in middle and neck positions), which pots should I use for best results?

Right now there's 3x 250k installed but humbuckers need 500k pots.
I've got volume and 2x tone control.

What disadvantage is to expect if I simply use 3x 250k???

If I add a 500k pot, which one will it be, tone or volume??