Matt I've had several soldered, one rare tank damn near had a full layer of solder underneath, talk about adding weight. Every time they were very rough inside so they received Re-Kote including the first tank I used on the racebike, a 400F. The rad shop always did the RedKote after they were dipped in their tank. Early on I ran a 50/50 mix of C12 & pump gas and never had an issue with the coating, but I always drained the tank immediately after the weekend. Clean interior and no lining or filter is king though!
Be forewarned about race gas, some are corrosive with combustion. Not sure, it may only be the leaded fuel but regardless it's wise. As soon as you're home use a remote tank and run the engine on some pump gas, then drain the carbs of that #$%*.
![Wink ;)](http://forums.sohc4.net/Smileys/default/wink.gif)
My experience was a delayed end of season teardown and difficulty getting the plugs out because of corrosion. Nearly ruined one plug thread. Now I heat it up on non race gas within a day or two.