Hi! ha3dy_j1s. Actually,the plastic weatherproof sheet is hard but flexible.It is primarily for Marine use. It will lay flush on the roof,with no gap in between. I do not want a raised roof rack or platform, making it more than 96''off the ground,voiding it PKWY compatible. White in color,it will protect+insulate from hot+cold weather. All the roofs recessed-concave corrugated sunken ribs and seams,will be filled with PVC-composite strips & silicone sealant,so water will not stand for any chance of mildew & rust. The 5' x 8' sheet will be held down in place between two 10' channels facing in to each other,bolted through the roof,on either side of the six existing nipples. Each rail rides directly over the three 1/2''tall roof rack placement points,serving as guides to keep the channel rails from compressing the cheap sheet metal roof,which is flush with the top of the 6 nipples. Sounds crazy,but I think it's going to work. The hard part was strengthening the existing super structure from the inside floor to ceiling.These vertical risers also offer support of storage cabinets. If interested, sometime take a nine or ten foot straight edge. I would recommend a 10' length of Home Depot super strut with holes,so you can see where it could be applied and attached inside or out-floor,ceiling,roof. I was an electrician,so I love kindorf. I have two 10 foot channels bolted to existing holes in the ceilings ribs,that serve as backbones. Later,3/4''EMT[Electrical Metal Tubing]slightly bent-contoured, 6-will be attached across horizontally to strengthen each of the three existing cross member ribs. Have already glued,screwed+bolted 1/2''+3/4''shaped plywood strips 4''x55'' across rear door overhead frame,covering oversized holes looking in wasted space behind clearance lights. I was very fortunate,to be able to compare the last two generations of Ram Vans next to each other. This new ProMaster's sheet metal is inferior to earlier vehicles. Great way to ruin the roof,just stand on it. That was not a problem with my last two vans. I at least layed a 4' x 8' plywood before testing. I could feel the stock roof and side walls flexing in + out,far too easy. Obviously,I have the time to go through all this trouble, wanting a second floor on my van. It has been a fun project. When completed,I will have 4' x 10'=40sq ft floor space inside,and 5' x 8'=40sq ft,available out on-up top. I will post pictures of the process.