i've never measured the wood web, but i think i usually take it to where a cross secioin of the finished product would be about half wood and half pewter. maybe a little less wood if anything.
this isn't chevroned, but gives some idea of the wood web I use.
first pic is before the top sides get tapered in.
2nd pic is with the tapers filed in (but before locking holes are drilled).
3rd pic: you didn't ask, but I've also tweaked Ken's excellent guide to include a paper towel tube as the primary form.
Slotted and rolled to as near your final dimension as you dare, to minimize pewter removal later.
You do of course want to leave some buffer, and you certainly will with a cylinder like this.
I secured it with a hose clamp and some tape on the seam, but it seems - in my mind anyway - to lessen the chance for a blow-through leak.
you can see I also put a little "sealer gasket" of modeler's clay under the bolt head.
Hot pewter going down the bore gives me nightmares.
let us know how it goes.
/mike millard