David, Keep practicing. Don't be concerned with your numerical copy speed (5 wpm, 7 wpm, 15 wpm). The speed will come. Hearing each character and deciphering it at 20 wpm character speed is what is key to learning now. After your brain has been trained to decipher what your ear receives consistently at 20 wpm character speed you can then work on copy speed by decreasing the time that each character is sent. For now, while in the learning stage, copying words rather than random clusters will only slow down your learning process. Copying words you tend to be lazy about what is being sent by anticipating what the sender will send next to complete the word. Randomizing what is sent trains your brain/auditory organ to decipher each character rather than clusters of characters that form a word.
