Oh, this is an enabling group of riders, alright....but for a first-time SS certification? Are you certain you're willing to invest the time and effort into getting an aux fuel cell on this specific bike
before you realize that either the bike doesn't work for this style of riding (for whatever reason...)
or you find out that 800 miles in, maybe LD riding isn't for you?
Not trying to be a 'Debbie Downer' here, but just keep shoving fuel into that 4.8 gallon (to dry, right?) tank, and plan 140 - 160 mile fuel stops.
I'm not certain that I'd make this any more of a challenge than it already is.
Remember the AOW about new farkles just before a ride...
Luck to ya!