What's Your Favorite Pad for Endurance?

I am shopping for a new saddle pad. I ride LD's in a barrel saddle, and have looked at Impact Gels, CSI's, and the PRS pads endorsed by Clinton Anderson. They've all received rave reviews from reiners, cutters, and barrel racers, but I'd like to know what other endurance riders recommend. Four hrs on the trail just doesn't compare with one hr in the arena. I've had some saddle fit issues this past year, and want something that will evenly distribute pressure and keep his back cool. I hope to do a 50 by the end of the year. My horse is a 15.3 QH, with hight withers. My saddle has semi-QH bars, but has left dry spots in the area behind his withers, in line with the cinch. I was riding in a 100% wool felt pad, but it's time for something newer/better. I'm hoping the proper pad with fix the saddle fit issues, as the saddle "looks" like it fits, and he was never sore backed. What are some favorites for endurance riders? Brand, material, inserts? Any personal stories would be appreciated. Thanks!