Ross,
If you are using a 1/2" ID hose, which is usually how they are identified (ID) then I think something else is wrong. 3/8" is pretty common in my shop and it powers everything using lengths of 20 feet and longer.
My info says that 100 feet of 3/8" hose will pass 25 CFM at 125 lbs. It looks like the average DA uses between 11 and 13 CFM. If these figures are correct, I don't think it is the hose that is strangling your sander.
Stuart
