inverter dc cable size

I am installing 2 Xantrex X-power 1200 inverters in a custom Sprinter van. I've never done anything like this before and could use some advice from experienced installers.

The installation instructions say to use 2ga wire for the + cable and 8ga for the - cable.

Two questions:

1. Why the big difference in wire size for the pos and neg DC cables?

2. Space for routing the cables is really tight. Would running 4ga + cables make much of a difference in the inverters operation? One of the inverters will be powering about 750 watts and the other only about 100 watts. I could splt the loads more evenly if that would help.

Thanks,

Inverter newbie

No the inverters do not have integral fuses. The instructions say to use a 150 amp fuse on the power cable to the inverter. A 400 watt inverter I have on hand has a 35 amp fuse. That would put the 1000 watt inverter at about 90(?) amps. The only reason I can see for a 150 amp fuse is to protect the pos. power cable and the vehicle battery. The inverter has built in thermal and overload protection. I really need to reduce the size of the positive cables.

Thanks

two reasons for 2 inverters:

the customer wants the option of powering a small fridge or microwave and these converters were the closest I could find price and power wise that had a remote on-off switch. Space is REALLY tight with no room for the large relays needed for remote switching.