They aren't mine, but here are some pics!
The big hole in the ply is for a leaf blower or shop vac.
It consists of a 46" ply circle, then a 48" xps foam circle, covered in plastic sheeting. The hole on top runs all the way through the foam, but not through the plastic. The plastic has 5 holes in it for the air to escape, approximately 8" from the edge. Lastly, there is a 24" ply circle in the center on the bottom to help form the skirt, secured by 7 bolts. One centered, the rest 60 degrees apart, 2" from the edge.
I hope that helps. It has been flown with a 300 lbs person on it, or two high school kids.
Just ask if you need any more info!
Now, I could go with a single motor for thrust and float or a dedicated motor for each function. The CF-2812 would be a zippy little motor for thrust. The 400, more power, less zip. My worry is that, unless I build a fairly heavy hovercraft, the 400 will be overkill for a lift motor. I think either motor would be plenty to serve the dual purpose role.
Now, what material for the skirt? I like the idea of using a durable, stretchable fabric. The material that Under Armor is made of should fit the bill. As luck would have it, my wife and I have a good friend who is a designer for UA, so I am pretty sure I could get some of that for free! (I have hundreds, perhaps thousands of dollars worth of Puma and UA prototypes and pre-production designs from this guy!) Heck, hate to do it, but I could cut of one of the many articles of clothing I do have. Also, I think a light gage neoprene would work well.
This would only need a single servo, but I'm thinking of putting an actuated spoiler on the front to give the nose down-force so it can really turn. Heck, these things are so simple, why don't we all build a single or double person model? They are the ultimate, multi-surface vehicle. Disclaimer: While capable of operating on nearly any surface, that surface must be flat.