They no longer have the #6507 cart that fits my Q120 and I bought this #6557 by mistake after reading a post incorrectly.  But once I got the cart I could not help to see how much off my Q120 would be to the #6557.  It nearly fit in the Q1000 slot.  There are ridges near the leg dock that was about the height of the amount I was off from making it fit, so I got out my Dremel with a grinder bit and took off the ridges on the left side only as seen in the pic.  Once complete the Q120 fit perfectly in the Q1000 slot and was nice and tight.