Asharrow has a good point. I approach the pyramid thickness differently, but it's true that an exact consistent thickness will make the pyramid bend more toward the handle, less toward the tips.
When you mark out the dimensions of a pyramid bow, since, as Ash said, you can't ACTUALLY, taper to a point, most guys just mark the sides, tapering to a 3/8"-1/2" wide tips. In this case you will need a slight front/back taper to make the limb bend evenly.
I usually DO mark the sides taper to a point. Then, I add some width to those last few inches with parallel sides. So, the side taper ends, say 5-6" from the tip, and the sides become parallel. This let's me not have to specifically try to taper the thicknesz, but as I tiller, I end up doing it anyway, working the bow toward tiller.
BTW, the best way to hit draw weight is to pull the bow only about that hard as you tiller. If you want a 50 lb bow, only pull the bow on the tillering tree with 50 lbs of force. Lots of guys use a spring scale to do this. I have a pulley system to watch limbs bend, but I also have a bar and weights from an old barbell set I hang on the string and step back. Early on this will only bend the limbs a bit, but that's ok. Correct what you can see, and check again. The weight will pull it 3", then 5", then 8", etc. By the time it's pulling a real string 20" or so, I'm usually happy with the bend, and just have to bring it in.
Lastly, "trapping", is the practice of reducing the limbs to a trapezoid cross section, the back being narrower than the belly, and the sides angled. Most woods are stronger in tension than compression, so you help the belly a little doing this. It also reduces physical limb weight while maintaining stiffness. You lose weight faster than you lose stiffness, if that makes sense.
On a pyramid bow, this might be used to take the weak inner limb/stiff outer limb problem. If you narrowed the back by 1/4" by angling the sides, you'd be removing PROPORTIONALLY more width at the tips, since the inner limbs are wider and the tips narrower. Handled properly, this might let you get away with less front/back taper.