Found a photo of Bill, Travis and Tu Lam, and you're right, though it's hard to be sure due to perspective, Travis looks like he's within maybe an inch of Bill's 6'4".
It's funny that you call him 'lean' though, (unless you meant lean as in 'not fat'), because he's fairly muscular.
It struck me how much perceptions have changed over the decades when I watched a couple of the older, Sean Connery Bond movies recently.
The 'big', dangerous, muscular henchman back then would be considered average build today, and less muscular/defined than many regular Joes who just lift regularly these days.
Another example is looking at photos of the average soldier from WWII to Vietnam, vs today.