Lisa's comments are here, https://www.guitartricks.com/lesson.php?input=21988 .
I have three very different guitars and I use a strap on each of them when I play sitting...which is all the time. :D With strap adjusted to allow the guitars to hang per Christopher's instructions I find each guitar is comfortable and stable. Without the strap I can feel my body tensing to keep/hold the guitar in place.
The way I held/hold the guitars didn't seem to have much effect on stiffness and soreness. That was cured long ago by concentrating on proper posture (also covered in the above links). Most of my practice sessions run two to two and a half hours...
Come to think about it...the instructors I had when I was a kid had me using straps too, also when sitting.
"It takes a lot of devotion and work, or maybe I should say play, because if you love it, that's what it amounts to. I haven't found any shortcuts, and I've been looking for a long time."
-- Chet Atkins
-- Chet Atkins
