What! Are you body shaming and calling a 400 pound person fat! How 1900’s of you... Just kidding. I just had a conversation with a doctor about how they avoid calling people fat now because the patient can cause so much trouble (sue, file complaint if not independent, leave terrible reviews...).The best answer is it depends on the condition of the roof and the condition of the walker. 400 pounds on an old spongy roof may not be the best idea. Moderate weight on a good roof should be no problem.
I got news for ya. The 35 year architectural shingles from 2005-6 were a POS as well. I have them on my house and I'm now looking at a formed on site standing seam. I expected it to be the only roof I put on the building in my lifetime.I remember the older IKO contractor grade shingles, despite the 20 year guarantees, they got pretty brittle around 15 years. They sure stripped pretty easy. Barely needed a shingle shovel.
I do hear him on VOM once in a while.I havent heard many great things about IKOs over the years except they are cheap. I have Certainteed architectural shingles on the house. They are basically double thickness.
I was getting my infrequent fix of Hot and Cold radio when heading over to an event yesterday and Tom mentioned the concept of painting asphalt shingles to extend their life. He has success stretching even deteriorated shingles. The logic make sense.
BTW if you are not familiar with Hot and Cold, Toms been doing it on Maine radio for 30 years. He is fellow Hearth.com member. Its in theory about Energy and Heating but definitely ranges over a lot of topics. Its a call in show but he starts out with misc rambling at the beginning of the show. His podcasts tend to lag the actual show dates. I am normally outside the range of broadcast in NH but when I head over to Maine on a Saturday AM I tune it in.