Ordered a replacement
Well, I did it: sold my 2417 Sport, and ordered a 2417KD. Thought the wife would like the sofa in the slide, but she preferred the dinette.
More room inside than the Sport. Plus, the dinette/bed is wide enough for a short adult to sleep in comfortably, instead of 6" narrower in the Sport model.
Lots of improvements over the earlier models. Bigger 'fridge, self-igniting water heater, 30-gal grey tank, bigger toilet cassette, to name a few. Can't wait to get it, maybe 4-6 weeks.
As for the tongue wt; 40-gal fresh water tank is in the rear storage area, and the battery is under the bench in the slide. Water in back will lighten the tongue wt considerably, as opposed to the KB model, where the water is up-front.