Is the plan formula integrated with SS or is it a new comp design something like where everyone is in their own group where you are dong the 401(a)(4) testing with permitted disparity.
Because if its the former it's pretty straight forward where every one gets 1 percentage on the base salary plus an additional percentage on the excess salary. So in your case it's possible everyone should be getting 12.93% base plus 5.7% excess and you look to the doc on 415 for the two owners who will go over the 415 limit and see what your document says in that situation. It may be refund of elective or it may be limit employer contribution.
If it's the later, you should be able to run the calcs through your software and see what you need to pass.
But as they say, when in doubt, read the document.