Jerry,i'm an advocate of POR-15,i've never been a fan of textured underseal,I imagine the rough surface would be more likely to give dirt and crud a key to stick.
I used POR extensively,here's a picture of the underside of my rear fenders.
I double coated them so I hope they'll be good for another 60+ years!

1950 Chevy Advance Design 3100 in Scotland
In the Stovebolt Gallery
More pix on Flickr.
I've definately got this truck thing in my blood ... my DNA sequence has torque settings
"Of all the small nations of this earth,perhaps only the ancient Greeks surpass the Scots in their contribution to mankind" Winston Churchill.