Sole Proprietor Employee DB deduction

[Guest RBlaine]

How does a Sole Proprietor split his contribution for deduction purposes between his employees for Schedule C and himself for 1040?

Is any reasonable method acceptable?

In the past, using IA, the NC for each participant is shown and, I suppose, you could allocate the contribution on that basis.

What about for PPA (or prior years where there was some amortization charges)? Still make estimates based on the NC of each participant?

I would be sure to include a caveat that this cost allocation should not be used in any other manner to mislead the employer or employees regarding the true value of their benefit, or somesuch.