Wonderful explanation, Francisco - thanks for taking the time to write
all of that out!

I still scratch my head as to why the Thomas book recommends such a
large Cl range for the horizontal tail, though. His example for a 15m
ship with some pretty common dimensions winds up with a tail Cl range
of around 0.67 to -0.73 at a static stability margin of -0.05 (pg. 136
to 139 of the Thomas book).

And regarding the positive lift on the tail: Your explanation makes
sense in light of the (basic) modelling I've done of spanwise lift
distribution... However the wing airfoil still exhibits a negative
(i.e. nose down) pitching moment. So something needs to counteract
that force - especially because positive lift from the tail would
amplify the nose-down trend. Are you saying that the CG is
sufficiently far aft that it provides the "counterbalancing force", to
put it in layman's terms? I hate to keep repeating his name (but his
book is the most comprehensive one that I've read) - however, Thomas
talks about "aft CG" a lot, and in his measurements you never see
anything further aft than about 50% of the MAC. And as a result of all
of this, doesn't a positive-lifting tail then limit your forward CG
position?

Thanks again, take care,

--Noel
P.S. My R/C gliders were so much easier - just move the battery (CG)
around until the plane was pitch-neutral with 0 tail trim! :-P