stryped wrote:
(snip)

Thanks so much for your informative post. My studds indeed are
irregular. My thought was to use full sheets untill they because
irregular in the spacing, then cut the sheets to fit the rest of the
studs.

....and you've just made a 10' butt joint. In fact, a cut edge next to a
factory recessed edge is worse than a regular butt joint. It makes more
sense to hang horizontally, as god intended. (why yes, it is a religious
issue.)

I never thought of your idea on the 1x3's but one problem I see
is the outlets would be way recesed if I used those.

There's no need to have 16" oc for walls. 24"oc is fine. If you'd like,
get the 1/2" high strength or sag-resistant board. (It is rated for
24"oc on ceilings.)