Take an 18” piece of para cord or shoelace tie in a loop and loop through the strop clasp and on the doorknob, with the door open. That will put the strop at waist height.
It is not about how tight you hold the strop, it is the downward pressure that rolls an edge. Light pressure, go slow, stop before you flip, flip with your fingers not your wrist.
You may as well get some magnification and inspect your edges, a Carson Micro Brite is $10-15 with a lighted 60-100x power. There are many posts on magnification and what to look for. A 12k would not hurt either based on how your “collection” is growing…