Leather being a natural material will never be perfect and changes with weather conditions such as humidity.
I use well worn DMT plates up to 1000 grit on my strops,they are dead flat when finished.
By using an X pattern stroke on any strop, you will get full coverage to the blade edge,thinking that using a wide strop and just up and down strokes is wrong IMO as the stropping surface changes all the time esp with hanging strops,Just my two cents.