Got to be honest, I didn't notice any hill at all...not even a slight one. What I will say is that if you end up near the back, or middle for the start of the return 1.5miles, don't worry about wasting energy trying to weave in and out in order to overtake. I did that loads and it's a waste of time, the oppurtunity to move up comes quickly enough. It is very narrow, most parts (all of it maybe) will not allow more than 3 lads alongside one another without somebody ending up in the bushes and if you have a great big group like on my PRMC (57 fellas) then you can imagine how easy it is to be stuck near the back for the first little bit.
On the same note, some people have said in the past how hard the warm up is for it but I thought it was exactly as you'd imagine, nothing to worry about at all. And the 1.5 miles out is very comfortable, and as this is what you should be replicating in training it will allow you to catch your breath IF the warm up had proved difficult.