I cut up my portable surge guard and attached it to (partly) the bitter end of the shore power cord, and then (the other part) to the power centre as a permanent installation inside the shore cord lockable storage box. Probably against NEC but who cares about those foreign rules ? (Except ours are probably the same!)
The OP could add his extra length of #10 by adding the one end to it, but also by cleverly adding the other end to meet the surge guard end at the bitter end where it joins to the RV power centre since it is already "cut".