Save yourself the time and get a set of mikuni carbs if you plan to swap a lot. 1 set of carbs and just change the dump tubes and needles around and you're good to go for either fuel. No harm in switching between the two, just like you said, its going to be a pain in the butt. Your timing plate will offer you plenty of adjustment for both fuels. The stock CDI box advances the timing a little bit already, so the +4, +7, +9, etc is timing added to the entire curve thats in the stock box. If you want a custom curve get yourself a dyna and program some custom curves in it, one curve for each fuel.