Do you have a barrel crimp or insulated connector rated 1000V DC to transition from #4 PV wire to #6? I am running #4 wire to minimize Voltage drop and the inverter lugs are rated for max #6.
Al Frishman Aeonsolar email@example.com 917 699 6641
Unfortunately, neither Hubbell (Burundy) or Polaris offer 1000V products. There are some 1000V splices at Amazon and Granger, and although they are rated 1000V, they don't look very robust. Heat shrink is usually rated by dielectric strength per mil of thickness, so it's possible that you could get away with a barrel crimp that had enough heat shrink over it to meet 1000V requirements - this in no way implies any UL suitability of course...
It doesn't help now, but I know that Polaris is about to release a 2000V line of products in the uncertain future.