:yup: Heaven forbid if you get rocks or dirt in between the two- it will act like sandpaper on your bed and do some wicked damage. My advice to you is to use your truck until you start scratching the bed up. When it starts getting bad, have a pro put the spray in on. Rhino liner and Line-x are the top 2.Definitely don't do the drop in. The bed of your truck bends and moves. As it does this, the drop in rubs the paint off and you will get rust. Good luck.
I have used Herculiner before, and after one Wisconsin summer, it had already turned an ugly gray and is getting powdery. Line-X turns a very subtle gray (the base-level stuff) after about 10 years in the elements up here, without any difference in durability.Definitely spray on bedliner kit is best. I have use Herculiner Brush on Bed Liner Kit. It offers a tough, polyurethane protective coating with extra shine. It prevents rust by sealing and bonding.