xf:message styling

I'm a value to change Show modal message Line 1. I am message 1's text.
Line 2. I am message 1's text.
Line 3. I am message 1's text.
Line 4. I am message 1's text.
Line 5. I am message 1's text. Show ephemeral message Line 1. I am message 1's text.
Line 2. I am message 1's text.
Line 3. I am message 1's text.
Line 4. I am message 1's text.
Line 5. I am message 1's text. Show modeless message Line 1. I am message 1's text.
Line 2. I am message 1's text.
Line 3. I am message 1's text.
Line 4. I am message 1's text.
Line 5. I am message 1's text. Changeable value?

With formsPlayer 1.5.4.1001. There are the following CSS problems when trying to style an xf:message:

Setting 'width' value for .pe-message-header has no effect;
Setting 'padding' value for .pe-message-header has no effect;
Setting 'margin' value for pe-header-text has no effect