You dont need copper with dispys. Copper is ran as a flat line pulling a spoon or flasher/fly combo. The weight of the copper line alone deopending on the amount out and speed can reach depths of around 100'. On my boat dipsys are a necessity. They acount for about 60% of the fish compared to the riggers. The wire your probably hearing about being run on the dipsy rods is generally 7 strand stainless steel. It is used becaus it doesnt stretch like mono does and cuts through the fleas easier. Some people run braid to eliminate the stretch but it seems like the fleas pile up on it alot easier and in greater quantity.
In my own opinion for your setup i would run your riggers as you do but with spoons and i would run the dispys off the sides with on a 2 or 3 setting with flasher fly combos so they're out away from everything. Any more than 4 rods on that size boat your asking for trouble.
Good Luck and post reports and questions! This is a great community and everyone on here is willing to share.