I'm hooked on HEED. Love it. Had trouble getting it to dissolve on my 300k when I filled my bottle with ice, but 15 minutes down the road seemed to do the trick.
I've had mixed luck with Perpetuem. Not sure I like the way it sits in my stomach.
I use Gu on the bike as my "food". So far mixing the Gu and the HEED is working. Stomached 14 hours of Gu and HEED on my last Brevet, with some solid food mixed in at the controls.
Want to find something like Perpetuem - but need it to sit a bit better in my stomach....
Off to ride the SS home, then on to the road bike for some hills!
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So long. Been nice knowing you BF.... to all the friends I've made here and in real life... its been great. But this place needs an enema.