"Look for the same Vmp"
Because: the MPPT controller "tunes" itself to match what it sees as the Vmp of the solar panels
, and if your panels have different Vmp values, the MPPT cannot work at peak efficiency. It will still work, but if I had to guess I'd guess
it could lose 5-10% power if the Vmp differences confused it badly enough to really mess it up. And I'd guess
that the impact would be less than that, since the four other panels would tend to swamp out any minor differences from the fifth, making a single-digit loss more likely. (Now, ask me to guess
which drawer your socks are in.<G>)
If you have to wait a bit to get a good match...how's your power holding up meanwhile?