Eric,
I would suggest that you approach presenting UL Backpacking as simply an option for him to consider vs. "THE WAY" to do it.
Tell him that it is just like technology….he can use it (UL Knowledge) to help him go lighter, but that he needs to know its limitations.
Yes, the gear is more fragile, but with a little more situation awareness and care, it won't be a problem.
See how he wants to hike.
If he wants gear that is tough as nails, then the traditional stuff will be the way to go, but at the expense of being heavier.
Find out how he wants to hike his hike.
Does he want to go off trail all the time or is he going to be on a trail the majority of the time?
If he is going off trail, then something like a dyneema pack might be the way to go.
He has a lot of skills under his belt, which is great and will help him go light to start with.
The big challenge is that he is accustom to a heavy load with gear that is designed for serious abuse, so light for him might be 40 lbs….all things are relative.
Show him the way and he will like follow you once he sees a value for himself.
Even if he uses just a few UL methods, it will help him lighten his load.
Then it will be like a virus, gear porn, countless hours of gear research, talking to crazy people on the forums, etc. :)
Tony