I looked at this model at a local dealer last summer and really liked the layout as well. As you mentioned the slide was a problem for me too. I don't know if it was the same problem as yours but it was two-fold for me.
First on the inside, the slide floor was a toe-stubber in front of the fridge and stove. I did not like how it stuck out into the main floor space with the metal edge. They should have ended it closer to flush with the appliances so you didn't kick into it or twist your ankle on it. Standing close to the stove you had to choose what level you stood on. With the transition zone being best for me my foot was half on half off the slide floor. Very awkward feeling.

Second, on the one I looked at, I could see daylight coming in all across the bottom of the slide. I looked at it from the outside and sure enough there was at least a 1/2" unsealed gap between the main floor and the slide floor. Yes it was fully deployed. A gap that big means heat loss or gain depending on time of year. I like camping during the winter so I could see snow drifts piling up on the kitchen floor on a windy day.
I really did like the floor plan but the build quality in the slide out turned me off on that model and probably any Denali product with a slide after seeing that. I wonder what the OP saw on their slide?
As far as surge guard I'd go Progressive Industries interior. Wire it up and forget about it, no worries about it walking off when your not looking.