[Dick Splash]

Gudday Ed
With that warped bit of wood, if it were me, I would wait a couple of weeks then have it re machined straight then glue the stock up asap. After it has settled for another length of time (as long as possible and def over a week) re machine it straight, then rout the rail, that way youll have more chance of keepint the whole affair straight.
I think the wood for the handle is just a matter of personal choice to be honest, theres hardly enough to make any noticable difference at all, you can let in some lead ballast when the gun is nearly finished, I think its best to make it all a bit bouyant and then balance it all afterwards, not that I'm any great authority on the matter, the first gun I made sank like a stone