I think you have your answer. I've tried the crap in a tube and the cheap cork as well with similar results. I've used the felpro for several years now, and even reused it several times when I had to remove the valve cover. It keeps working and at this point has paid for itself.
1991 YJ, rebuilt 4.0L in spring 2009 at 234,000 miles, no lift yet, slightly offset wheels, 235/75/15 tires for now, rag top, sold the hard top. Over 35,000 miles on the rebuild and counting.
2006 Jeep Liberty. Nothing special, all stock.