Dalescarpentry,
Just a thought on the tapered barrel channel.....Assuming you are using a router table, if you mounted the forearm blank to a tapered piece of wood, with carpet tape for instance, then routed the channel you should get a tapered cut in the forearm. The unknown here is the amount of taper, probably trial and error, but once you get the tapered carrier right you could re-use it.
Roudy