Ais6 not supported for all valid dac values (e.g. dac=200 and fi=3).

[mb12]

Here is a sample message to reproduce the issue. This one has dac=200 (AIS_DAC_200_RIS).

!AIVDM,1,1,,A,602E3U0rFKsn<P<j07,4*5A

An option might be to just have an Ais6_X_X where body is stored verbatim.