I've tried this too but the farthest you are probably going to get is NREM2 or 3. You can physically tell when your body falls asleep it feels like going down a 'level' or you'll feel a rush of energy which will then stay with you until the next rush. Those were my experiences with trying this, I'm pretty sure I haven't got past NREM2 without falling asleep, I did a WBTB one time and it worked perfectly just use these same techniques when you do it. You'll probably have one