Hi Ron,
You are getting good advice all around. I hope what I add has some value to you. I started (as many of us did I am sure...being the "sharpen monkey" and "rough planner" for the "Elder Wrights," Now teaching it to others and watching them develop their skill sets has done much for me improving mine.
1) LN vs LV? Any preference as they apply to planing timbers?
The quality of LN and any good vintage plane has a charm and affect that is wonderful. Japanese planes also are a much favored tool of mine, yet for recommendation to the "work horse" and what we use as a hand driven "power planner," there is little that will beat the versatility, technically adjustable, and interchangeability than a good arsenal of Veritas planes. They really allow those new to planning by hand, and "high volume" planning excel!
2) Ideally, I'd like to get by with one plane, Lie Nielson #4-1/2 or #5-1/2? Can I? Should I? I have a friend that uses two #4's in the process, each with a different shaped iron. Makes sense to me, but since I'm just removing the bandsaw marks off the timber, would one plane work?
You can use just one plane, and that was the traditional method for the "Barnwright," and many "Bridgewrights," as well. That would be your Scrub Plane and/or #4 with a heavy camber, taken across the grain at a 40 to 30 degree angle (though I have seen others.)
3) How much to camber the irons so as not to leave tracks?
30 foot circumference is what I was taught, which always made me laugh at how I was suppose to achieve that... I tell students that you really need to see what your own body, the plane and the wood you are working tells you. It will very, but as Dave S. stated, make in a very clean arch.
Do you guys think a 5-1/2 is too long?
No, it all depends on what you finish goal for the timer is. We start with a scrub to "rough in" the timber and may stop there, or it could go all the way to scrapers around knots, and jointing plane. With the Veritas you can use the same blades in several tools interchangeably and the new alloys-though hard to sharpen-take a razor edge that last a very long time. As stated, "keep them keenly sharp and your work will be much less the effort for it."
I like the idea of one plane with two differently shaped irons, although if the process really dictates that two planes are needed I would get two.
You can use one as stated or as many as 4 or 5 it all depends on the finish goal and what your client is seeking from you.
Should the finish iron just have the edges rounded a bit?
No...that is more an affect of some Japanese planes, yet many of them also have a subtle camber as well.
Good Luck!
j
