Putting on my boat owners hat on, I would not be buying a boat with slideouts. The #1 rule in boating is to keep the water on the outside. It is common to see large sections of the sides of motoryachts able to open outwards forming a dock/platform to launch various water toys. These are all hinged well above the waterline.
The links show a home brew & a production toon. From a saltwater boat owners perspective aluminium is nothing but trouble. From a boaters perspective in general all of those moving parts can't be good for the structural integrity of the boat.