Help me with the math here... What multiplier would I use against bike weights, to calculate that bike's change in tongue weight? What's the TWM (tongue weight multiple?). I realize the bike's position on the tongue is also a factor, so presuming I could potentially do 4 bikes that's a separate variable for each; TWMa, TWMb, TWMc, and TWMd.
Bike*TWM = change in tongue weight, resulting from the bike.
So what I need to do is predetermine what I want my tongue weight to be unloaded (or with 1 propane and 1 battery), then estimate my TWM variables for each bike. Then I can work through scenarios loading from 1 to 4 bikes and calculate their net effect on tongue weight. Seems simple enough, right?