I gave my 8 year old son a ride once. I almost had to pull over due to my arms shaking with exhaustion trying to hold him up after 30 min. I took my wife for a ride once, just to dinner and back. Went into the garage afterwards and removed the passenger pegs and put the cowl back on and the packed them away for re-sale.
It's doable, but its not fun. I would buy a Diavel if I wanted to give rides. The 1199 is a solo race bike in my mind.
Sorry that doesn't help, but this bike was never intended for that kind of weight or load. Mine got hot with just my son on the back for a few minutes. it needs to be run fast and that's just not safe with two up. Unless both parties are geared up, have the skill, and willing to take that risk.
I've seen a couple that run the tracks on the 1199. It's impressive, but for every day commuting...not so much.
The next time my son rides on my bike, he will be driving.