Why pay back some of the money at all then? If you are knowingly scamming the system (and the lender) you don't take out a $2,000 loan, just to pay back $400 before declaring bankruptcy.
The 4 on-time payments make it look like you tried to pay the loan back but just couldn't afford it.
If no payments were made at all, it would be easier to prove that there was intentional fraud. If such is proven, it may be impossible to wipe the loan during bankruptcy.