At the lower end you can use the foot cradles to assist a regular bar pull up Certainly the rows will help to gain the strength to weight ratio to a point where pull ups are more feasable Try overshortening the TRX so that you are able to sit underneath the handles and pull up from here. Once you are...

Watch this video to learn how to configure the TRX using a Dual Point Anchoring System for exercises like pull ups, dips and muscle ups.