thisfits asked: I'm kinda in the same boat as diogenesdoesargentina, the athletic build chinos guy. He should check out mainline Lands' End Tailored Fit. Good fit through the thighs with a modest taper below the knee. The waist measures 1" larger than the tagged size, so depending on how he likes his fit, he might want to size down one. There's a pretty good thread on reddit's /malefashionadvice subreddit right now that shows fit pics, just search the frontpage for "big thighs".
There you have it. I’ve got chicken legs so I’m rarely in a situation where I need to search the internet for ‘big thighs’. Thanks, Aliotsy!