When we bought out Grand Design Imagine XLS 21BHE, GVWR of the trailer is 6,395, the dealer didn't have an 10K/1K equal-i-zer WDH in stock and tried to sell me a 12K/1.2K WDH. I contacted Equal-i-zer directly and got the following response:
"Both of those hitches would be fine. They are correct in saying it isn't too much hitch. You can size up to the 12k model. The good thing about it is that they are adjustable to fit each size of trailer. So if you got a larger or even a smaller trailer later on you wouldn't need to switch the hitch. Chances are they just have 12k models and not 10k and they just want to sell you what they have in stock. In this case that is totally fine and you shouldn't have an issue with the 12k model."
So I have a 12K/1.2K equal-i-zer hitch installed and it works fine.