It's a tough one. It's always going to be a bit of a compromise, it'll never sound exactly like two Strat pickups - one coil of a VHII is less powerful than an Irish Tour, and (of course) the magnet structure is totally different.
I was going to suggest the same as Phil, swapping the humbucker wiring around so you're using the other coil in the split position. But then you'll lose the hum-cancelling effect in that position.
Other than that, I wonder if a more powerful HB might work better? I wouldn't know which model to suggest though.