DIY carbon and GFO reactor

I decided I want to start running a GFO reactor and why buy when you can build right haha. So I have an extra RODI unit laying around its old and a POS so my plan is to drill it out and add pvc to both ends and remove the mombrane housing. then just add a couple sponges in there and it should be about set. I will add a gate valve to the input so I can adjust the flow coming in. It should work right I don't have any experience with reactors but by looking at the pictures it looks like it will work just fine. Ideas? Also since it has a third chamber should I run something else besides just carbon and GFO? Thanks guys! As always I appreciate any and all help or comments