Idea for improving plate pinch

Two methods for improving ones own plate pinch records.
I haven't tested this yet, so it's experimental.

1
Doing for example 15 and 20 kilogram together
-15 at thumbs side and 15 at pointing, middle, ring and little fingers side.
And later 20 and 20 kilogram
And then 25 and 20 kilogram
-25 at thumbs side and 15 at pointing, middle, ring and little fingers side.
And then 25 and 25 kilogram

2
First doing for example 2 x 15 KG plates wich have a slight ridge.
And then doing 2 x 15 KG plates which are completely flat or completely flat if both outsides are out.