I'm guessing you are hauling with the rear seats and midgate up, so the 8' sheets extend beyond the tailgate. One way to haul sheets
I also have an XUV and have hauled a multitude of building supplies and 4 x 8 sheets (up to ~10) of most anything in the back. If you fold the rear seats forward and put down the midgate window and then the midgate, you can then put down the rear tailgate window and fold the tailgate down to have a platform well over 8' long to carry sheets.
I use a couple 2x4s full length or just a few blocks stacked down the center of the cargo floor to support the center of the sheets and then load them using the shelves on both sides of the cargo area and the tabs on the base of folded rear seats to support the front of the sheets. You can even use the driver side auxiliary tailgate support at 2 different levels, one to help support the tailgate flat and one slightly elevated to support the rear edges of the sheets at the level of the sheets.
Even if you want to transport longer lumber or longer sheets supported by longer lumber, the flat tailgate support level will assist in carrying all that weight on the tailgate.
As a homeowner (not a contractor), I have remodeled multiple homes to varying extents and prefer my closed/convertible XUV that hauls similar to a pickup over most pickups. With the roof open and tailgate down I've hauled tall furniture, mattresses and other oddly shaped items that won't fit in a regular SUV with a liftgate.
As an added bonus, my SLT has the air bag suspension in the back and only once have I overloaded it to where it would not re-level the vehicle after loading. I usually leave the vehicle running while loading so the compressor keeps it level and does't work as hard later.
It's a VERY versatile vehicle and I don't know what I will do when it comes time to replace it.
) My 2003 Envoy listed out for about $35k.