I once fished for northerns with a 9' 6 wt and tossed normal sized pike flies of 6"-9" with it without problems. I used a 7 wt floating shooting head and flies tied on Sealy 3/0 4XL hooks (a hook that has not been made for many years, unfortunately). However, the flies were tied long through the use of whole saddle feathers tied pusher style on the rear of the hook, Aunt Lydia's Rug Yarn for a body, a saddle hackle palmered on the body with a few extra turns at the front, and .035 lead wrapped on the front 1/3 of the body to get a jig-effect on the retrieve.
I was able to cast them 60'-70' with the 7 wt floating shooting head because, as was mentioned, the flies did not hold water. I was returning from trout fishing and the fellow I was with wanted to try and catch a pike because he had not done so before on a fly rod. He had an 8 wt along with his 6 wt with him; alas, I only had my 6 wt. I did have a few pike flies stuffed in my fihsing vest though.
I found it is very possible to fish with even a 6 wt for pike and be able to cast a large pike-sized flies (provided they were made of materials that did not soad up and hold water) with it. The rod was nearly worthless for pumping in pike over about 8 pounds though. I did manage to land one of around 25 pounds that day; but it was no fun on the 6 wt. I would never pike fish again with anything smaller than an 8 wt.