The issue is not only related to [Stock First Period], any [INVT].[Inventory input] and [INVT].[Outputs] correction in the middle year month will require recalculation of the month's after the affected month.
The proposal is simple: users just enter data for [INVT].[Stock first period], [INVT].[Inventory input] and [INVT].[Outputs] in the input form (may be with some Excel formulas to simulate the result). Then after saving data the DM package for the full year scope is launched by user. Over year transfer have to be done using another DM package!
Nothing in default.lgf related to this process.
Vadim