I am a fly fishing instructor. You can put the split shot wherever you want. Distance from the fly generally doesn't spook the fish. I've used split shot directly in front of the fly, but generally 12-18" above the fly is where must anglers place the split shot. You can also leave a tag end on your tippet knot, and place the shot on the tag end so that if you snag up the shot pulls free, and you do not lose your fly. You may have to put an overhand knot in on the tag end to stop the shot from pulling off too easily. How you cast is a biggie on getting down. The speed of the current, and depth is a big factor and can't be judged here. Casting up, and not too far out, stripping in slack as the line moves back towards you will bet you the deepest. Casting straight out, and with some distance in fast water, and you may not be able to get down using a lot of lead. Strike indicators not only telegraph the strike, but more importantly allow the leader, and wt below the indicator to get your fly down deep without using that much lead.