I too have beefy thighs. Beefier than anyone else I've ever met, as a matter of fact. I’m 6’1 and at that weight the timberlines worked great, though I don’t think you’ll squeeze a base layer underneath - not comfortably anyways. It would have to be really damn cold for that anyways. My walking around weight is 210-220 and the TLs were a touch too tight in the thighs and seat for me and I sold them off.I’m 6’0”, 31-32” waist, 190 lbs. I have beefy thighs. Looking for input on the Timberline fit. I’m thinking about 32R, but not sure if there’s room for a base layer.