You can adjust this parameter:

Scoring:
  --mp <int>,<int>   max and min penalties for mismatch; lower qual = lower penalty <6,2>
  --sp <int>,<int>   max and min penalties for soft-clipping; lower qual = lower penalty <2,1>

I would suggest a parameter sweep where you run multiple tests with different values to see how it affects mapping.

One consideration too is that hisat2 is soft-clipping reads, so you may want consider adjusting those options as well, You can see the scoring option above. There's also an option to disable soft-clipping entirely..