How to read 32-bit float with ModbusMaster lib?

With the function of reading holding regiseter in ModbusMaster, I can only read 16-bit register once, but the float uses two 16-bit registers, so how can I read it?

result = node.ReadHoldingRegisters(2, 6);

  // do something with data if read is successful
  if (result == node.ku8MBSuccess)
  {
    for (j = 0; j < 6; j++)
    {
      data[j] = node.RX(j);
    }
  }

the lib is here: Arduino Playground - ModbusMaster Library