I agree with getting a TIG welder to bond all of the segments together and then weld on a bond plate. You could then use a tin coated copper crimp connector (Burndy, T&B Color keyed) to connect the copper to the stainless. We have been using this method with great success. The first thing to go will be the copper, so protect it with a layer of paint or sealant until it is covered with insulation or gets out of continous contact with the water. We use 1/4-20 316SS or 304SS bolts with copper anti-sieze on the threads and can then easily remove them down the line if needed. Aluminum will likely melt away nefore your eyes... Aluminum is one step above zinc on the galvanic series...
