if 7 jsa team members are in a serpentine line they get the defense of the highest character in that square correct..

yes

From the FAQ
Defend may work with more than two characters, as outlined below:
ABC
“A” has Defend; its defense is 18. “B” has Defend; its defense is 17. “C” does not have Defend; its defense is 15. “A” can share its defense with “B,” making “B’s” defense 18. “B” can share its defense, now 18, with “C,” making “C’s” defense 18 as well.

JSA works the same as the Defend power

From the DC FAQ
The Justice Society team ability is transitive in the same manner as the “Defend” superpower described in the General FAQ, except that it can only be used with other Justice Society team members.