Oldest person you met or knew that started the sport late?

I not going down the whole weight BMI rabbit hole. I have no reason to doubt your point that your weight reflects a muscular build. My point is slightly different 5'6 is just very short for a 168 fighter and short for a 160 fighter. Canelo listed height is 5'7 and a half. He always stands out as remarkably short for this weight range. Although, I sure someone will find exceptions I think short fighters age face more challenges as they age. Your foot speed will inevitably decline as you get older which is just going make it more of a challenge to close the distance. To gop back to the Tyson example I don't think he was never going the late career of someone like Lewis, regardless of prison and lifestyle, as his height made him more dependent on speed. The average in shape 168 fighter is likely to be about 6 inches taller than you, your going to need to be technically excellent with high boxing IQ to effectively cut of the ring as a very short fighter in their 40s .

A friend of mine and myself done some fairly light sparing in our local club in our 40s- we both had some amateur experience from almost 2 decades earlier. To be honest I coped a lot better then him despite being in worse shape as despite being only half fit I am 6'6 and could use my jab maintain distance. He was a shorter inside fighter and his style just proved when he lost his athletic edge.