Welcome to FlyerTalk, Wolfsrule20. There are actually two threads here in the Southwest forum that could be helpful to you to get data points on how things have gone for others with EBCI and without it:

Post your boarding card # for EB (Early Bird) checkin

Post Your Boarding Card # (non EarlyBird, A-list or BS)

These (and many others) are also listed in the Southwest Wiki Thread, which you might want to check out if you haven't already: Southwest / Rapid Rewards Buzz : the official Wiki Thread