What fee limbs I have done, I have found that no matter how I clamp the pads to the bottom of the limb butt, the glue or clamp pressure will leave it not dead level . You can see this when you block sand them. Even with a block or a belt sander , how do you keep them square?
Right or wrong, here is what I do and it seems to work pretty well.
After gluing up and taking my limbs out of the form, I will remove all excess with my belt sander. Then I add my phenolic to the bottom of the limb butts. After that sets up, I sand the limbs to width on the belt sander.
I lay both limbs side by side on a flat surface and clamp the butts down. If my layup was good, the tips will be perfectly side by side and even. If not I try to measure as best I can , how much the pad needs to be cut to get them even.
Then they go in my mill supported by parallel bars. I have a digital angle gage and get them level on both planes. Tedious...each limb is marked and I always measure and work from the fixed side of the machinist vise. Then I use a large carbide end mill, surface the limb, and drill the limb bolt hole and pin pocket before the limb ever leaves the vice.
Next limb get the same treatment but pointing the other direction and this is when one becomes the top and bottom.
Then I check them clamped side by side again, if good, they get bolted to riser, then centerline is marked using my laser level on a large table.
The laser is visible the entire length of the bow and riser.
Then I cut the limb profile.