I sure wouldn't take the ceiling down if you don't need to. I found a few leaks (about halfway up a segment seam) by using an air nozzle. This works good on endcaps also.
Get the "needle" attachment for your air nozzle. Remove a pop rivet from one of the inside seams near where you want to check. Set the air regulator very low, so that you get just a few psi coming out of the nozzle.
Insert the nozzle into the rivet hole, tape the trigger open. Spray the outside seams with soapy water and I think you will see large bubbles where there are leaks.
Of course if the bottom of the inside sheets are hanging loose, you may want to tape them in place with masking tape ot duct tape. You don't need to make them airtight, just enough to get a little air pressure between the skins.
I tried this and it works.
If you have exposed seams, you can run a length of duct tape along the seam and test it the same way by putting the air nozzle into the tape. Just leave the tape a little loose directly above the joint.