Marc,
Don't get me wrong, I understand the benefit of double categorization to the seller, but as a buyer, it doesn't help me personally.

Listings without thumbs would definitely benefit.

Another option that would benefit browsing the ads would be to keep the listings for the different categories posted on the left hand side of the page at all times. Right now, if you go into Airplanes, you can no longer go into Engines without first going back to the main Marketplace page. This again makes the browsing experience take longer as you must do this for each of the sections. I browse Engines, Airplanes, Plans, and Radios. To do this, I have to hit the main Marketplace page a total of four times instead of just once. Believe me, if I could get a faster connection, this wouldn't be so much of an annoyance, but I'm stuck with a blindingly slow 24K connection due to my choice of living in the sticks

Thank you,
John