Go to your dealer (on your next oil change or whenever you like), tell them that the e-brake feels loose, and ask them to tighten it.

It's warranty work, so it'll be free.

When I got my ProLX, you really had to pull up the ebrake for it to hold, and even then, it didn't hold well.

Somebody posted before that if you yank the e-brake at speeds of 25+, the rear wheels should lock. I couldn't get my wheels to lock before, after tightening at the dealer, I can now.