try a stripping basket, maybe even one of those collapsable ones, make sure your line is clean, and maybe you need a faster or longer rod. A diferent line may be the answer as well - i never could cast the whole line on a 5 wt, except for when I used a sage TCR line, and that was only in the grass and never in a fishing situation, even from the boat. Only other thing I can think of is check how you are hauling, the shorter the strokes the more effiecient they are - try keeping your left and right hands as close a possible while hauling.
WF 7wt on up I could cast a whole line from the boat. Wade fishing I could cast a whole line with shooting heads but was usually on the rocks. Now, put yourself in a fishing show setting with a casting pool and no wind or obstructions to worry about, I'm sure you could do it. Lastly, maybe take your rod to orvis or SG and see if one of the staff can watch you to see if anything can be improved upon.