A few days ago i saw two different 4e sumps.
Pity i didnt take pics.
The glanza one was more tapered on the left side,easier to be baffled.
Since the oil travels to the left when cornering,its better to weld the plates on the left only.
Just a thought,if you weld the plates all around then the oil takes more time to run down to the sump.
It could be a few seconds more. Im only extrapolating here,no hard evidence at my disposal regarding the time taken.
Welding is a cheaper alternative.
This is what i have done to my sump [ partly welded where its more prone to allow oil to "climb" during hard cornering ]
I used your picture to give an idea.
Hope you dont mind.