How to increase stream rate in pixhawk on output telemetry?

I want to get telemetry RAW_IMU and ATTITUDE from pixhawk (telem1) by arduino. In mission planner or QGC, I can put stream rate in intervals from 0 to 10 Hz. In actual I can get 5-8 Hz from telem1. I wish to increase the stream rate. I try to increase data rate by arduino function mavlink_msg_request_data_stream_pack(… , uint16_t req_message_rate, …). The function changes rate value in a list from mission planner, but the real value is not changed.

#include 
#include 
    SoftwareSerial _MavLinkSerial(10, 11); 

      // Mavlink variables
      unsigned long previousMillisMAVLink = 0;     // will store last time MAVLink was transmitted and listened
      unsigned long next_interval_MAVLink = 1000;  // next interval to count
      const int num_hbs = 60;                      // # of heartbeats to wait before activating STREAMS from Pixhawk. 60 = one minute.
      int num_hbs_pasados = num_hbs;

      

    void Mav_Request_Data()
    {
      mavlink_message_t msg;
      uint8_t buf[MAVLINK_MAX_PACKET_LEN];


      // To be setup according to the needed information to be requested from the Pixhawk
      const int  maxStreams = 1;
      const uint8_t MAVStreams[maxStreams] = {MAV_DATA_STREAM_ALL};
      const uint16_t MAVRates[maxStreams] = {100}; 

      for (int i = 0; i < maxStreams; i++) {
          mavlink_msg_request_data_stream_pack(6, 200, &msg, 1, 0, MAVStreams[i], MAVRates[i], 1);
        uint16_t len = mavlink_msg_to_send_buffer(buf, &msg);
        _MavLinkSerial.write(buf, len);
      }
    }



    receive_imu() 
    {
       
      mavlink_message_t msg;
      mavlink_status_t status;

      while (_MavLinkSerial.available() > 0) 
      {
        Serial.println(msg.msgid);

        float c = _MavLinkSerial.read();

        if (mavlink_parse_char(MAVLINK_COMM_0, c, &msg, &status))
        {     
         /* if(msg.msgid==30) // #30: ATTITUDE
              {
                mavlink_attitude_t attitude;
                mavlink_msg_attitude_decode(&msg, &attitude);

               }
    */
          if(msg.msgid==27) // #27: MAVLINK_MSG_ID_RAW_IMU 
              {            
                mavlink_raw_imu_t raw_imu;
                mavlink_msg_raw_imu_decode(&msg, &raw_imu);
               Serial.println(raw_imu.zacc);                
              } 
          }
       }
    }

    void setup() {
      
      _MavLinkSerial.begin(57600);
      Serial.begin(57600);
      Mav_Request_Data();

    }

    void loop() {

      receive_imu();
     
}

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