So the Husband is teaching the teen Sunday school class for a few weeks, and has been working his way through the "5 Solas." As his wife, I get to sit in. Good stuff. He's reviewing the basics of his lessons [on his now deleted blog] once he's taught them for class. You should go read them.
Sola Gracia is the big sticking point in Fundamentalism, isn't it? We say we're saved by grace through faith, but we sure don't preach sanctification by grace through faith. Nope, sanctification is by works, don't'cha know?? *rolls eyes*
In retrospect [speaking from my perspective in 2012], this Sunday School series my husband presented was the touchstone for his journey out of our local church. There had always been annoyances in Fundamentalism, those "minor" things that were made into "major" things, but the study that went into this series highlighted doctrinal things that we differed on. Emphases rather than substance perhaps, but differences nonetheless. As the years progressed, it became more apparent just how foundational those differences were.