on one hand the plate will no doubt help but on the other hand have you now not made the problem worse by making the sump even lower to the road.
My thoughts exactly and then some... As well as what's already been mentioned my problem is this:
5mm is a lot in your case, plus the thickness of the protruding welds that are now easier to catch in area's that weren't before now.
The sump plug is vulnerable
Looking at the new one surely this area has the exact same risk and is even more likely to be caught now.