4000, my customers do, or I sure wouldnt bother with thickness. Liners are a breeze once you do em for awhile, trust me. Do what works for you, I wouldnt worry about what others think anyway, lol. Swamp, heck I dont mind, I just couldnt take credit for the quote, let someone smarter then me have their due...right? Ok, then that could be about anyone, hahaha.