regarding summercoinv2.conf file mine is the default one and contains the default rpcuser , rpcpassword.
should we change this? as I have not and its what ever came with the download wallet file.
Last question what is RPC 
Who is running their NavajoCoin Wallet in the most power efficient way .
I wanna go way low, how low can I go
The remote procedure call (RPC), give a interface to external program (or remote
computer) to interact with the your wallet, to give at it commands and get
from it some responses.
Normally the user of the GUI Wallet, don't need to use it explicitly, can more
simply use the debug\console windows without the need of other permanent
settings.
But in a more complex scenario, like nogui Linux wallet demon, or solo mining,
or other integrated service (IE payment platform, block explorer etc) , then
in this case you must use the RPC, and You must give to the wallet a set of
secret setting like RPC User\Password\Port\AllowIp for autorize the incoming
connection only to you, and your programs.
Otherwise, if you don't have previously locked the wallet, an external user could
give at your wallet some nasty command, like transfer away all your funds.
So if you don't use RPC, don't worry, but if you must use it, then use long
user\passoword and keep it secret.
Regarding the power waste, I think the Raspberry Pi (a lilliputian micro sistem)
plus a external usb memory card \ hd, can be a valid solution, but i don't have
any direct experience.
Here someone else can give more information than me.
Bye Bye
