Just realized I need to put the #wpsp-1234 at the beginning of the css line, not the end.
Problem solved. Closing the ticket.
#wpsp-1805 h5 {
font-size: 16px;
font-weight: 400;
line-height: 1.2;
}
#wpsp-1805 .wp-show-posts-entry-header {
border-top: solid 1px #cccccc;
padding-top: 10px;
}
