I have the fly rug and they are not very generous I am afraid to say. We bought a 6'3" to fit our 15H QH (she is 6'3 in all other rugs) and she is not a very chunky build like some. we thought great it will fit a QH bum !! but sadly it didn't. In the end we had to have a rug swap around and put it on the 14.2 QH. One I put it on the mare I went back to check the bag to see if they had send me the right size as it was that small. ???
I quite like the premier fly rugs, we have one in 6'6 for our 15.1H QH who is slightly on the 'plump' side. I have a 16.2 Danish WB and he is wearing a stateline tack fly and gnat rug which is awesome, but sadly they have stopped shipping to the uk at the moment as they were bought out. If you can get one of them I think you would be happy with it (we have two)
THe rambo QH nylon sheet is nice though