I found that following the directions was not sufficient when I tried copper. I had a test and it usually read the copper levels as 60% of what they needed to be if I followed the directions. I would highly recommend a test if you're going to use copper.
In answer to your question of hyposalinity vs. copper, I think that copper is probably the better solution. Hyposalinity sounds better on paper because it's less stressful on the fish and on your pocketbook, but it's much more difficult to execute. If you have too much evaporation one day and your salinity jumps a point or two, you have to start all over. Copper is much easier.
92-gallon corner tank, 100lbs of LR
, 140lbs of sand, 250watt 10,000K MH
, 110watts of actinic PCs, Mag 7 return, custom refugium, AquaC EV180 w/ Mag 5
Female lyretail anthias, eyelash blenny, tomato clown, saddleback clown, firefish goby, 2 sand-sifting stars