Here is the prep I have .

synthesis of Supported TCEP Resin 1. Three hundred milligrams of 1.14 mmol/g loaded ChemMatrix resin was swollen in DCM. TCEP·HCl (98 mg, 0.342 mmol) was dissolved in DMF containing DIPEA (117 μL, 0.684 mmol). HBTU in DMF was added dropwise (130 mg, 0.342 mmol), and the mixture was allowed to react for 5 min. Then the mixture was put onto the resin under mechanical stirring for 24 h. Resin was washed with 3 × 10 mL DMF (3 min), 1 × 10 mL HCl 1 M (3 min), 1 × 10 mL methanol (3 min), 1 × 10 mL Et2O (3 min), 2 × 10 mL DCM (3 min) and finally dried under vacuum. About 320 mg of resin 1 was obtained. The loading was calculated from data obtained by phosphorus elemental analysis performed by inductively coupled plasma-atomic emission spectrometry (ICP-AES). 1.30% (weight) of phosphorus was detected. The loading of TCEP-CM 1 was determined as 0.42 mmol/g. 

I am seeking to have resin 4 % covalently bonded .