While I prefer a 7wt, I've gotten them on my 5wt often and even a couple on the 4wt.
With the 4-5 wts I use a straight piece of 8# mono, with the 7wt 15# test (I don't exactly coddle them!)
The flies already mentioned are all good, depending on where in the water column the fish activity is.
I find them much more energetic in the summer, now or right at ice out they are fairly lethargic.
Better a Dragonrider than the Dragon's slave.