Ok, so that is not what I expected. Let's look at the math....
A string of 5 of the 355W panels will have a voltage of 5 x 39.1V = 195V, and a current of 9.09A.
A string of 5 of the 365W panels will have a voltage of 5 x 34.3V = 171.5V, and a current of 10.65A.
If your buddy puts 2 strings of 355W and one string of 365W panels in parallel, the voltage of the combined array will be the lowest of all the strings, which would be 171.5V. That is, the lower voltage string holds the voltage down on the other two. The currents would still add up across the parallel strings, so he'd get 9.09A + 9.09A + 10.65A = 28.83A. That means your total wattage 28.83A x 171.5V = 4944W. The total wattage available from all the panels before you hooked them up this way was (10 x 355W) + (5 x 365W) = 5375W. So wiring them up the way you described causes a reduction of 430W, or about 8%. It's still more power than you had with just the 2 strings of 355W panels, so maybe it is worth it. It shouldn't cause any problem (assuming your SCC can handle the voltage and total power).
Note that all this math is based on Vmp and Imp of panels, which is based on Standard Test Conditions (STC). Rule of thumb is to assume the real world production of panels is 80% or so of STC.