calories for the distance
I have used heed and perpetuem for several months. They have been part of my routine for two double centuries. I like them because of the lack of simple sugars. I needed something that was simple on my stomach and wasn't just pumping sugars. I have used bottles with thick perpetuem and a camelback with Heed. I often dump the Perpetuem into my drinking waters. With the combination I do not need as many stops.
I also just tried spiz on a century. Worked well.
J