it occurred to me that rather than migrating ILS charges by creating FOLIO loans, aka POSTing to /circulation/loans, it might be less complicated to simply check the relevant items out to the relevant borrowers via /circulation/check-out-by-barcode and follow up with /circulation/loans/{id}/change-due-date to modify due dates as needed
one of the benefits of this approach was the opportunity to test the circ rules to make sure that I had gotten them right 
however, of the 4,898 lines in the chargeData db two did not load because their itemBarcodes could not be found in FOLIO 
it turned out that the relevant titles did not have holdingsRecords either and that both should've had Dewey call numbers that begin with zero - this was the clue that I needed to discover that I had left a line out of the bibLoad.pl script for 0XX call numbers that are in the STACKS - now I'm going to cp bibLoad.pl zeroFix.pl, edit zeroFix.pl so that it considers a list of catalog keys rather than every MARC in the db, pull a list of relevant catalog keys from the ILS, and then double check to make sure that Bob's my uncle...