The  Land Rover Discovery 1 and 2 Tough Touring Gutter mount roof top tent racks are  secured by 4 Gutter mounts each side as per Pics above - Running off a 1 piece gutter rail that extends the length of the Disco's roof. 
The  newest version of the Tough Touring rack comes standard as an 'INFOLD' as per majority of roof racks - where the of the rail is folded inwards to look good with a central 5 degree fold to increase the curve on the large footrails. 
 
Plank Lengths are 1400wide standard (ID 1220 )
Standard Roof top tent rack comes with 4 top hat Bar Planks included for easy tent installation and removal. 

The Tough Touring One Piece  Roof rail design takes away point load issues with traditional gutter mount roof racks, securing immense loads stronger and lower.  The testing run is shown here (Version 1). Its super strong and Super low, the roof tent sitting just 10mm off the roof at the rear of my truck. 
So far  in testing I have noted that the Wind noise is there, but not really any more noticable than the growl of the All Terrain tyres. Quite OK. The 'Hump' on the disco does compress the air coming up the bonnet somewhat. Positioning of the rack closer to the back of the truck eliminates majority of wind noise overall its a quiet rack. .. 

These Racks are being fabricated 5 at a time - to allow customers to buy them we have to list them as 'IN STOCK' on the web page here. Any order made that is not delivered inside a  month time frame is able to be refunded no questions asked.