As mentioned before, ride the STP as you've trained - eating and drinking with what you trained on... Nothing like having the stomach rebel on you while on the road because you ate or drank something you're not accustomed.
Another thing I learned this year is to not be intimidated by other riders - especially those in pace lines. I ride a trike, I'm a pace line of one, if you are going to pass me, better do it before we crest a hill. I can and do speed down hills at over 40 mph (this year's top speed for me was 42 mph) and I'll pass you like you're standing still (although hearing "what the hell" does make me smile). Going slow up hill does not equate to be "being slow". My overall average was 18.4 mph, Seattle to Centraila my average was 19.8 taking a little over 5 hours. The second half, Centraila to Portland, I averaged 17.0, taking just over 6 hours.
This year I had my fasted STP ever - taking 12 hours 20 minutes total to reach Portland from Seattle!
Doug
http://www.crazytrike.com