Peter,
you might consider taking the Rockwell Pass from Tyndall Basin into the Upper Wright Lakes Basin. From there you go up Mt Tyndall. It has been over 50 yrs, but I climbed Tyndall from the upper Wright Lake and do not remember any serious problems as it was indeed a Class 2 climb. You mention climbing down Tyndall south ridge to Wright Lakes and then to JMT. By going over Rockwell Pass you could leave the heavy packs at your campsite and go up the SW ridge with only a day pack and return to your camp. From there you would continue down to JMT. This would avoid carrying heavy packs up Tyndall and still keep you on your intended route to JMT.
