Working w&b balance calculations for our Texas trip; it will be the first time carrying the whole family at one time. We are within the envelope even with full fuel, but I'd prefer the cg to be further aft, which caused me to ponder the 100lb rear baggage limitation and the reason for it. At first I thought maybe it was an issue of that part of the fuselage not being built as heavy, but it occurred to me that the stabilator must apply much more force than that when you're loaded to forward cg. Also, there's no real limitation on weight in the aft seats, although the line in the chart stops at 450lbs. I have two sub-100 lb girls back there, so it seems like a few inches from the datum can't make much difference, structure wise. So is it a matter of the strength of the floor? Is it the strength of the plastic bulkhead? It would certainly spell disaster if something broke through there into the tail. When we took the Big Tylenol to Florida last year, we had <100lbs baggage, so it's an academic exercise, but I am curious as to the reason.