LiveCycle Designer ES2 - validation pattern and limit length: max chars

I am new to using LiveCycle to design forms.  This seems like it should be a really simple thing, but I am stuck on how to do it.

I have a Zip Code field.  It is set for both Zip and Zip + 4 Display and Validation Patterns.  The  Validation Pattern is text{99999}|text{999999999}.

I have a script that stops the entry of alpha characters.  I would also like to prevent users from entering more than 9 characters.  I would think the

Limit Length:  Max Chars:  feature would take care of this....but it doesn't.  I can't turn on the Limit Length because I get a warning that it conflicts

with my pattern.  Doesn't make sense to me because my pattern has a max of 9 numbers and I want my Limit Length to have a max of 9 characters.

I know I can use the pattern validation to provide a warning error message that tells a user to enter either 5 or 9 digits, but why can't I just stop them at 9?

Any help would be appreciated.

Thanks!