Sounds to me like your experiencing hot spots on your forehead due to an ill fitting helmet. Certain manufacturers make certain shape helmets, ie, round, oval, intermediate oval, round oval etc. I got lucky, and my schuberth E1 is made for an intermediate oval, which is my head shape. Maybe look into getting fitted by one of the helmet manufacturer reps at a rally or bike show, they are usually at these event
I do a fair amount of IBA rides, mostly BBG's (Bun burner gold-1500+ miles in less than 24 hrs). In fact I'm headed out on one tomorrow night, western ma to grand island Nebraska. I keep sour chews in my tank bag as stated above and every once in a while pop one in my mouth while riding. IBA rides are all setup to be done safely and legally within the time limit without speeding. I wont advertise my speeds, but usually finish a BBG around 21-22 hours. From what I've learned from the IBA rides and from a lot of my IBA friends is to minimize your time spent at stops(around 10 minutes) and avoid caffeine as its a diuretic that makes you have to urinate a lot. Your average speed for a successful ss1k can be as low as 42.5mph to complete it at 24hrs, 62.5mph for a BBG at 24hrs. Basically the trick is to keep the wheels spinning. If you gotta stop for break, do it, before its too late! Plan your ride and ride your plan!!
If ya ever need a witness, I'll gladly meet you anywhere in the northeast to sign it for ya. Always cool to put a name to face, and **** I'll go burn up the road with you on my GT!