True, but they need to be exactly the same length if you do. For some reason most of the places I read online seemed to frown on using smaller cables together like that..I don't know exactly why. It seems to me, it should work fine if the cables are the same length . The only place where it may get tricky is that ANL fuse on the Positive... would you use 2 smaller amp ones ?
I do know that some of the "larger " inverters recquire 2 power and 2 ground of smaller gauge. They do this as they "cheat" to make the inverter bigger. For instance they may be marketed as a 4000 watt inverter.. but in reality they are 2 each 2000 watt inverters in the same unit...so need a positive and ground for each.