Even if your hip pads are not tight, there could be issues with how you fit in your boat(s) that make your leg go to sleep. Part of the issue is that modern boats put you in a really weird knees-splayed position that is not natural for your body. The main culprits I've found are:
1. having the front edge of the seat sides press on the sides of your thighs because your knees are too far apart in the boat. This can be really subtle and gave me problems for years before I figured out exactly what the problem was.
2. having the front edge of the ass portion of the seat press into the backs of your thighs because your knees are too low in your boat.
The solution is often to figure out a way to build up foam that keeps your knees in and up. Not only does this relieve the pressure points that can cut off circulation, it also puts you in a more natural sitting position and can relieve a lot of other weird muscle tightness from paddling, as well as being way better for your low back/SI joint.
There's a tutorial on how to build knee blocks on our website if you scroll to the 4th item from the bottom. These will keep your knees up, and you can probably figure out how to modify them to keep your knees in as well if you're a little creative with the foam and glue.
Of course some stretching or yoga is a great idea too, because sometimes it's tight muscles and not just your seat restricting blood flow when you get in your boating position. We have a DVD for that action:
Good luck getting comfy in your boats!