I just built a bow that had 9" total PLam starting at the handle and extending 4" past the fades. These were placed over the handle under black glass and were of the same core as the 1st lam under the handle (They are barely noticible this way). They ran from .80 to zero over the 9" length so I used a .009 sled to run my tapers.
The tips had 7" Plams that went from .30 to 0 and I used a .007 sled for that.
All a Plam does is add stiffness in a limb forcing it to bend exactly as you want it to.