How long and what density is your sinktip? In heavy flows and deep water, a 13 ft. Type V might not do the job, that's why so many steelheaders build their own lines. I generally try to let the line get things down, weighted flies are nasty things to cast, could that be part of your casting problem? A shorter leader will help to keep your fly closer to the bottom and last but not least; mend, mend, mend.