Don't Pack a Sectional Warp
A bunch of us weavers were chatting, and not one of us knew why, when you use a sectional warp, you do not need to pack the layers with paper when you are beaming on. Why is that?
You don't need to pack a sectional warp beam (as long as you make sure that each layer of warp goes into its section like a flat ribbon of evenly spaced threads, filling the section entirely) because there is no way that any of the threads can drop out of their layer into a lower layer, disturbing their tension.
We pack the layers of warp on a non-sectional warp beam because it is very hard to achieve the even, tight, and complete spread of the warp threads that would keep all threads in their proper layer, especially the edge threads, which drop off the outside edges of the warp and therefore go on at a smaller diameter at the edges if there is no packing. The pegs in each section prevent the "falling off" of these edge threads. Even with a sectional beam, if the warp is very open and very long, it is possible that the threads won't pack evenly in each section. In that case, sectional beamers can insert sticks as they beam (since the pegs prevent inserting paper).
(Someone once showed me a method of beaming a non-sectional warp that made each successive layer on the beam narrower than the last. They warped back to front, sleying the warp in a reed instead of a raddle. Then, as the warp went on, they slowly changed the angle of the reed out of parallel to the back beam so that the changed angle of the reed made the warp narrower and narrower. The new positions of the warp threads kept them from cutting through the layers, and the narrowing edges prevented threads from dropping off. I thought it was clever.)