Just picked up a closeout Hydros 9 wt tip flex myself. (Exactly the same blank as the Helios, but with a different paint job and hadware, according to a former Orvis wholesale rep I spoke with.) The mid flex will do okay, but I think you will want the stiffness of the tip flex to handle bulky flies in the wind and pull strong fish out of the rocks and current. I have a softer 9 weight that I can coax a cast of 65-70 feet from on a calm day in my backyard, but on my first few tries with the tip flex I threw 90' without even working hard and the whole 105' fly line with just a little more effort.

On the other hand, if you're not a very experienced caster and have trouble throwing a tight loop or a good double-haul, the mid flex will be more forgiving.