[Erik]

Sedate, please consider that even a 5 metre improvement beyond a Personal Best is very large. Best Practices (based on observed accidents and successes) states that we should move down a metre or 2 at a time, over a longer period of time. So a 10 metre depth improvement over a PB might take 2 weeks of diving every day for example, or longer if it's challenging.
We've seen some bad lung squeezes that have eliminated freediving from a few peoples' list of activities.
We've also lost friends here for various reasons and it's not pleasant.
Good luck and take your time- freediving is not racing!
Warmly,
Erik Young