Passing on my experience using Terminal C's Pre✓ to clear security for Porter, who is now Pre✓-enabled and usually uses gate E2.

Porter's boarding passes, either paper or electronic, will not scan at the Terminal C scanners ... even though they have the Pre✓ logo on them.

You'll need to schlep over to Terminal E to transit security, but will receive "expedited" screening (i.e. you get to keep your shoes on, but everything else is exactly the same as non-Pre✓).

If it's an early morning flight, you'll probably get through security in E faster than C even if Pre✓ worked at C. Not much happening in Terminal E at 5:30am, at least on a Monday; C, though, is a mad-house at that time.