Footlocking the tail is indeed laborious cuz of the 2:1 thing plus if the rope is in a natural crotch you get the friction problem to boot. I footlock the doubled rope which makes for a 1:1 ratio, easier locks and no friction.
The Kong double would do the same as doubled Petzls, I think.
I get past the 30' burnout by using a tether that's short enough to rest on. It makes it so you can take a brief rest between every bite or you can just hang for a bit without worrying about having to unjam your prussik. It's not anywhere near as exhausting as footlocking competition style. By the time I get into the tree and tied in, I'm ready to work even after going 50' or 60'.
Of all the stuff I've learned about tree climbing, I think footlocking doubled rope with ascenders has been the most valuable.
JZ, about yer knees, make sure you're close to and parallel with the rope, toes down and KNEES TOGETHER before pushing up. Don't push while your knees are out to the side. Look at some of your pictures of folks like Rob or John or James footlocking and note how vertically oriented they are when pushing up. I'll try to post some later.