The original order is sediment, carbon, carbon, RO, RO then DI.
Sounds like you want to convert the second carbon canister into a dual DI which is easy enough to do with a few fittings and a little time.
If you do that, purchase a better 0.5, 0.6 or 1.0 micron sediment filter and carbon block as the 5 micron versions they come with are pretty coarse and you are eliminating the sacrificial carbon block.
You will need to replumb the second carbon canister by removing the nylon nipple between it and the first carbon lid so now the first carbon OUT line leads up to the RO membrane IN, then through the membranes and back down to the DI which you have replumbed and into the final DI. It is actually easier than it sounds.