Pulling larger cables into batt box

[openroad118]

I'd like to change over my existing batts to 4 6V AGM's, connected by new 2/0 cables. If I utilize the existing batt box, with height adjustments, the batt cables are smaller, possibly defeating using 2/0 on everything else. Has anyone tryed pulling new cables thu existing sleeves? I'd guess the street side sleeve would be more direct with less tight turns. I'd use existing cable to attach the new ones to, and use as a pull tape.

Watdya think?