Hey Chappy,
I feel your pain. I too bought the compact diesel about a year ago and had the same problem. Great strong frame and engine, but crappy cut. Mine was leaving the 'strips' you mention. The dealer and I did everything we could to no avail. He even took it in and gave it back to me saying it was solved, and when I got the mower home and measured, all he had done was lower the deck in the rear about 1/2" lower than the front. Not what BB recommends and not good for cutting anything thick.
Long story short, there is a work-around. Thanks to this forum, I found a guy who said get a set of Exmark blades. I did and if you hold the Exmark blades on end next to the BB blades, there is a tiny length difference. The Exmark's are a tad longer. It made a huge difference. It is still not perfect in my book, but much much better. If I had it to do all over, I would put the money I spent on the BB into a Kubota or something else. I wanted a diesel and the BB was the cheapest diesel I could find. It's a good operating mower, it just has one of the worst cuts I've ever encountered right out of the box. Try the Exmark blades, you won't be sorry you spent the money. :licking: