Plan Changing from Fiscal Year to Calendar Year

I have a plan that is a profit sharing only plan that has a plan year end of 11/30 and corresponds to the Employer fiscal year.  However, the employer is changing to calendar and wants to change the plan year to calendar year.  There will be a short plan year from 12/1 to 12/31.  They do not was to make the discretionary profit sharing for the plan year ending 11/30 but would rather make the profit sharing for the entire calendar year.  I think filing deadline has fried my brain.  Is that possible? If so, what are the steps to make that happen?

A one month plan year is going to have a really small 415 limit.

If you've got individual allocation groups, why not "rig" the amounts for both plan years to be the total they want to give out, and deposit the total on the 11/30 records?