Can I get a value of CMRR higher than 74dB using only ADS1298 (internal RLD Buffer)?

I've developed our pcb using ADS1298.  The highest value of CMRR obtained was 74dB. The entering signal is  Vpp=16V and 60Hz. In ads1298's datasheet said that it has a CMRR of -115dB but in "SBAA188-july 2011 Improving Common-Mode Rejection Using the Right-Leg Drive Amplifier" 3rd page says this: "....If 1% precision external components are used and the bandwidth of the RC filter is approximately 6 kHz, the system then has only 74 dB of CMR at 60 Hz ...". so my question is: Can I get a value of CMRR higher than 74dB using only ADS1298 (internal RLD Buffer)? 

What Can I do to improve the CMRR ?

This is our ADS1298 register configuration:

#define CONFIG1 0x86// 0x06 //Lower power mode         //1000 0110   0x86 high resolution

#define CONFIG2 0x10 

#define CONFIG3 0xDC//0xDE//0xDC//

#define LOFF 0x03//0x03//0xF3//0xE3//

#define CH1SET 0x00

#define CH2SET 0x00

#define CH3SET 0x00

#define CH4SET 0x00

#define CH5SET 0x00

#define CH6SET 0x00

#define CH7SET 0x00

#define CH8SET 0x00

#define RLD_SENSP 0x03      // 0x06//

#define RLD_SENSN 0x01     // 0x02

#define LOFF_SENSP 0XFF    //  0x00

#define LOFF_SENSN 0x00    // 0xFF //0x02 // 0x00

#define LOFF_FLIP 0x00

#define LOFF_STATP 00h  //read only

#define LOFF_STATN 0x00 //read only

#define GPIO 0x0F

#define PACE 0x03

#define RESP 0x00

#define CONFIG4 0x06

#define WCT1 0x0a 

#define WCT2 0xE3

Thanks in advance.

Migue