I presume that the custom tip series is the same as the wet tip express series, but I am not 100% sure...... Anyways I have the SA 275 grain saltwater wet tip express. I do a lot of pike and walleye flyfishing and love that line when the fish have moved into 5 - 12 feet of water. I like the saltwater tapers for pike fishing as these lines are designed for longer casts with larger flies. The saltwater wet tip express has a 32 foot head compared to the 25 foot head on the freshwater wet tip express. I do put this line on my 7 wt on occasion, but the 32 foot 275 grain head is a bit much for it so I normally fish it with an 8 or 9 wt rod. I would think that the 250 grain (25 foot head) freshwater taper would be a real nice match up for most 7 wt rods. And yes, these lines are density compensated lines with a heavier tip, a graduated density transition and a floating running line.
SA also makes a true full sinking "Uniform Sink" which is also DC, but truthfully I have never fished one so I better not comment. I have fished several of RIO's DC lines and without getting into details, I do like them as well.
PS. I used to try and flyfish in water deeper than 12 feet, but came to the realization several years ago that flyfishing really is best when kept at a shallow level. You can fly fish deeper than 12 feet, but I don't like to be outfished by the gear guys,,,,just too hard on my ego!!! So I move "up" in elevation or latitude to where I can find cooler water temps and shallow minded fish!