I am running 4/0-4/0-2/0-2 mobile home feeder cable 220 feet from a 200 amp meter to a 200 amp Exterior load center (Main Breaker). I will then connect to a 125 amp subpanel inside my cabin fed from a 125 amp breaker. Here are my questions:

1) Can I use 2" Sch 40 PVC for this service cable?
2) What size cable should I use from outside 125A breaker into the interior load center lug. Distance is about 15 feet, but the 4/0 is to big to connect to the 125 service panel lugs.
3) Do I connect the #2 green ground cable on the mobile home feeder to the Neutral in the Meter socket, run it to a rod or don't use it at all and ground the main breaker?

Thanks for any help!

How about a little more detail?

#1 depends... what is "type" of wire the feeder cable is? (letter designatiopn) For example, THHN would be OK, while RHW would require 2 1/2".
#2 A 125 amp circuit would require a #2 copper wire.
#3 The ground and neutral can oly be together at the first service connection. This is usually where the first disconnect is located, usually in the main panel. After that, all subs must have the groud bus isolated from the neutral, and a grounding rod must be used.
Does this help?

Thanks for the help, but am still confused about the ground wire (RHW - Aluminum 4 wire) that is with the 2 Conductors and Neutral. Where do I connect this ground cable at the Meter socket? Do I connect it with the neutral or to an earth ground rod?

My main disconnect is at the cabin (220' feet downstream). Would it be better to add a main breaker at the pole with the meter and ground it to a rod there? This is the only way I can make sense of the ground cable that is included w/ feeder cable.