Mobility for Tall Lifters
Mobility issues can only be solved by training for increased mobility. Most of the time people do this type of training unloaded, in a dynamic fashion. Nothing wrong with this, but as a guy who's pretty damn mobile for his size (6'4" and about 250), my squat form with an unloaded bar still looks much less pretty than it does with a loaded bar. Why? Because resistance forces the body to undergo a loaded stretch. As such, paused reps can be vitally important to tall guys.
People usually credit paused squats for shutting off the stretch reflex and stopping any momentum or transfer of forces so that you can train true strength from the bottom up. Well, in addition to that, paused reps can really help with bottom end range and ingraining proper technique.
Spending a few seconds in the hole on each rep can have a huge impact on how sturdy you feel at the bottom of your reps. That's invaluable for a tall guy who has the propensity to shift too far forward when back or front squatting. Anywhere from 2 to 5-second pauses are acceptable.
Stay tight while holding the bottom position. If you don't yet have the mobility to get down low, work within reasonable ranges until you develop it. The second you allow laxity to enter your joints by "reaching" for added range of motion is the moment the movement becomes unsafe.