anteverted pelvis

Neither. I am trying to help people tip just their pelvis forward, accompanied by a curve very low in the spine at a place called L5-S1. If you are not used to curving here, it is hard to isolate that place and the technique you describe probably isn't going to get you there. Tucking as far as possible doesn't do anything for pelvic anteversion. Worse, it can do significant damage to the discs in the lumbar spine, especially L5-S1. It may feel good because it stretches the lower back muscles, but it puts a lot of pressure on the lower spinal discs in the worst possible direction. I don't recommend extreme tucking for any purpose and certainly not for trying to get your pelvis well-situated. Extreme arching usually causes excessive curvature in the upper lumbar spine and doesn't necessarily affect L5-S1 at all. It usually takes training to arch back just the pelvis and not the upper lumbar spine. Most people doing this exercise will just be swaying their back in an unhealthy fashion. Again, there is a potential downside to this. Apart form training your low back to arch (a habit you want to train youself out of), if your lower spinal discs bulge or herniate, this action is risky - you are in danger of herniating or sequestrating (pinching off) a fragment of the affected disc. I did this to my back about twenty years ago and don't recommend it! Then we come to the "midpoint" position. I don't think this is a very precise guideline. Most people will just return to roughly what they started with after having done a little damage at both ends and reinforced some unhealthy movement patterns of tucking and swaying. L5-S1 is not trivial to isolate. This is why In 8 Steps I take people through the process of Stacksitting and Side Stretchlying first, where you have an implement (a wedge or your bed) to help you maintain your pelvis in a healthy position while you sort out any sway that has crept in higher up in your lumbar spine. Once your brain and your muscles are familiar with this anteverted pelvic position, it becomes easier to find it in tallstanding. Still, I have people go through the process of doing first a small squat so gravity can help you tip your pelvis forward (without any muscular effort on your part) and then backing out of the squat trying to leave your pelvis in the position gravity helped you settle it into. You want to relax into this position, not try to tense your way there.

It depends on whether your body is used to going to the end of the range of motion or not. Since it sounds like you are used to this, it should cause no problem (see yogi B.K.S. Iyengar's extreme backbends with all the bending happening at L5-S1). for people who are new to pelvic anteversion, I recommend proceeding gently and progressively since rapid change itself can cause inflammation.