Beware of maximum limitations. Keep in mind that contributions must first be allocated to the MPPP. Thus, if aggregate limits are exceeded, the prototype SEP contributions are limited/reduced (e.g., the $40,000 limit). Beware, most,
but not all prototype SEPs permit their use with a qualified MP plan.
Assume a 10% prototype SEP and a 15% MPPP. The total contribution can not always be allocated 40/60. For example. With compensation of $200k, owner receives $30,000 ($200,000 x .15) in the MPPP. Only $10,000 may be allocated to the SEP. Here, 25/75. If the MPPP were integrated with Social Security contributions, the SEP contribution wd have to be smaller or non-existant to be effective. If this type of a situation exists, care shd be taken so that the employees do not receive any more than they have to (by adjusting the SEP contribution to provide the owner with a specified dollar amount).
Assume a $40,000 MPPP contribution, having a SEP wd not provide owner with additional retirement plan contributions, deductions would increase, perhaps too loyalty; but at what cost(?).
Hope this helps.
p.s. Appleby, Butler, and Belgarath are correct.