In the Wally Marshall rods, I don't think the IM rating is the weight of the rod. IM is a technology use to describe the weaving or the way that grapite is put together. If you're going to need to lift fish into the boat with your rod, then I would suggest using a blank with some fiberglass in it. Bear in mind that I am biased here.I've fished with bamboo, fiberglass and graphite. While graphite is much lighter, by far my favorite is fiberglass. It can be limber, strong and sensative all at the same time.
Where you go is less important than how you take the steps.
But don't forget the Roadrunners