Please share you tips/instructionals you've found, on how to make sure you don't get thrown from standing rear naked choke position.

I was talking about martial arts with my colleague, who's in his early sixties, but is an absolute tank, 110kg, 6'2, former paratrooper, basketball pro and an amateur boxer... We were discussing fight strategies and talk came to rear naked choke. He told me it's impossible to do it to him. I am quite confident in my ability to ground people when already having aplied rnc/seatbelt. Said that I'm ~90kg. I asked for demonstration and applied a weak RNC without intent, looking to see his defense and he just reached back lifted me off the floor quite high, with a forward bend, where it was obvious he could have flipped and thrown me.

I was considering hooking the leg, but i've 0 amateur wrestling experienced and I don't particularly trust my bjj takedown fundamentals. Please offer any input on how to prevent any instance of this kind of counter happening from standing rnc/seatbelt position