blueman wrote:
I need to replace some isolated clapboards on our 100+ yr old house.
The exposure varies from 4" to almost 5" meaning that I probably can't
use regular 6" cedar clapboards (with actual width of 5 1/2").

So my plan is to buy 8" clapboards and rip them to width.

What is the proper (ideal) amount of OVERLAP that I should leave?
What is the MINIMAL overlap that I can leave?
(i.e. width of ripped clapboard minus exposure)

Since your patching in "isolated" individual boards into existing older
work, I'd match the existing spacing as closely as feasible.

When ripping should I be ripping from the non-tapered end then?

Assuming you have sufficient thickness when you're done. If the
originals weren't at least reasonably close to a present standard, you
may have a problem in that the bottom thickness of the new, wider
clapboards is at best no thicker than the existing so when you rip it
down you'll be noticeably thinner than the work you're trying to match.
In that case you may simply have to either make do with a poor match
or have some new siding milled to match dimensions you have. If you
need a reasonable amount, it probably wouldn't run much more than the
8" by the time you figure the waste, it might be the same or even less
plus a better fit/match and less trouble, to boot. On the old barn,
couldn't find 3-1/4 T&G of same style so went the route of having 2000
linear feet milled for the job. Takes knowing what you're looking for
to tell where it is except in a couple of areas where there are sizable
areas of all new.