Expense reimbursement from surplus

I'm assisting with a DB plan termination.  Perhaps there is a prior discussion thread on this topic, but I’ve been unable to find it.

The termination process will include purchase (by the plan) of a group annuity and lump sum offers to as many participants as possible, and then execute the formal termination.  The best guess is this will result in a 7-digit surplus. 

First, the sponsor has paid expenses (actuary, auditor, attorney, etc.) directly (from the company, not from the trust) for many years.  Prior to executing the formal termination, the sponsor wants to use up some of the surplus by having the trust reimburse the company for as many of these expenses as possible.  So far, we see nothing in the document that will prohibit this.  However, is there any limit to this?  Could the trust reimburse expenses from the prior 5 years?  10 years?  More?  Do you know any prior examples or PLRs that might address this?

Second, our assumption is that any such reimbursement is NOT a reversion.  Is that a reasonable conclusion?

@david rigby  this link may take you down memory lane: