Affect on late deposit of PS on 415 in a pooled plan

[BG5150]

I know that if a PS for a year is deposited more than 30 days after the ER's tax return is due, then those amounts are annual additions for the year in which the deposit is made.  (Let's assume a calendar year plan and tax year)

However, what if it's a pooled plan, and some of it was already deposited timely?  Do I prorate the late amount across the participants?

For example, there are $25,000 (out of $60,000) from the 2015 PS allocation that hasn't been deposited yet.  For 2016, the owner is due $40,000 between deferral, SH and PS (under 50, no catch-up).  Is the owner's portion of the $25,000 prorated over the 2015 allocation?  (If he was going to get 40% of the 2015 contribution, then $6,250 of the $25k is slated as an annual addition in '16?)

[K2]

I think you revise the prior year's work and allocate a contribution of $35,000, taking into consideration the plan terms, THM, gateway, etc.  I don't think a proration works.  

[BG5150]

Thing is, the late deposit makes it a 415 annual addition for the year it is depsoited, even though it was based on 2015 allocation overall.

[K2]

But it hasn't been deposited yet, you said.  So if and when it's deposited, it could be either a 2016 contribution or 2017 contribution, and the person or persons, and source or sources, and year or years, should be spelled out when contributed, or in some cases put into a prefunded contribution account, and I'm not fond of those.