Head position - When your head is turned to breathe, it is very well positioned level with the water, turned only enough to get a breath, and making a nice bow wave for your body to go through. Work on carrying your head at that level the whole stroke, because in one video, just before you breathe, you lift your head up to mid forehead - stop that. In your final video (labelled "f") your head holds a very good level. That is where you said you wanted to try your old stroke technique. Recovery - Your recovery is smooth and relaxed, but your hand position is too high - get your hand below the level of your elbow on the recovery. Also, keep your left arm straighter longer on the recovery - you are pausing your upper arm halfway through the recovery so you can swing your lower arm forward. Put another way, throw your whole arm around and let it fall out in front of you, rather than aiming for a controlled landing. Body line - Hard to see from straight on. We need an overhead or underwater shot to see if you are staying straight. Catch - Your arms are entering very well at shoulder width. You have a good wide catch, with no crossing over. Great! Your Right arm is catching fantastically, holding a high elbow while you swing your forearm down. You are using your left arm to support your breathing, so you are starting your left pull straight armed and pushing water down to lift your body to breathe. You do not want to lift your body to breathe - that is wasted up/down effort. So <b>...</b>