5th Panel... sort of
This is a work around to the limit of four panels view sets. If you need more than four, you can create tear off panels. In any of the standard viewports, select the camer you want to make into a new panel viewport. Then select Panel>Tear off copy...
Once the new floating panel appears you can safely switch the original viewport to a different camera.
AIM: mhcannonDMC
"If you love your job, you'll never work another day in your life."