Our Tec-to-Rec package is designed for XR divers who want to occasionally enjoy recreational single-cylinder dives. As experienced tec divers will tell you, using your large twinset wing with a single cylinder creates undesirable drag and also affects your trim. Instead, better to use a smaller wing optimised for single-cylinder diving.
Since you already have your own backplate and harness, all you need is a smaller wing. This will give you a streamlined configuration which translates into less drag, less effort, and less gas consumption.
You should consider adding a Harness Adjustment Ring. It makes a big difference to getting in/out of your harness easily.