Doug, Thank you, as always, for your thoughtful answers!

I normally space holes about 2"
apart, but there's no hard-and-fast rule about that.

Do you mean 2" between centers? Since "straight-up" is the best way to
exit my subpanel, I wish to be efficient. I've already planned 8 cables
coming out, with others likely to follow. Putting two 10-2 cables in a
3/4" hole and two 12-2 (or 14-2) cables in a 5/8" hole ought to be
efficient! I'll follow the same grouping rules threading the wires
through the wall studs. Lew Hodgett pointed out that threading three
10-2 cables through a 3/4" hole was definitely wrong. I would appreciate
knowing his point of view concerning this.

Is there any problem with different gauge cables sharing the same hole
(I considered that the conduit on the lesser cable might not be adequate
to be next to a hotter cable)? Swingman (smartly) advised me not to do
anything I don't feel confident about--and this is a detail that makes
me hesitate.

My concern was that the location was
where someone might expect to find a light switch (so I would use a
coverplate, or equivalent protection).

Not sure what you mean here.

If I walked through a door and reached around for a switch only to feel
an outlet I would find it a little unnerving. I was thinking of the
types of coverplates that have additional "child-proof" covers over the
outlets or that are designed for exterior use ("spring-loaded" outlet
covers). At 50" inches, I would have 4 duplex outlets in a neat row.
"Form" may have to sacrifice for the sake of "function" here though,
and I may move that outlet down to knee-level. That outlet will allow
me to easily plug in an extension cord for use in the back yard and will
be a big improvement over my existing configuration. I'll save the idea
of exterior outlets for another year.

THANK YOU (ALL); having "Fun"!
Bill


BTW, is anyone else not sure they prefer the appearance of those "flat"
GFCI outlets compared to traditonal-looking outlets. The former seem to
be styled for use in a home. For $32 (x3), I can buy GFCI C-Breakers,
and use the outlets I like, but I'd just soon have the GFCI switch at
the (first) outlet. Maybe I should get around a little more and try
shopping someplace besides Menards...but based upon what I've seen, I'm
not going to get my hopes up.