As part of our implementation for Xtuple, one of the key requirements was to value the stock using FIFO rather than the methods offered by default in Xtuple. After migrating from Netsuite, this became the next major task in our implementation. It took almost a year to develop, initially the first release took around 5 months, but it was only after many rounds of fixes and tweaks that we finally got to a situation where it would correctly calculate the stock valuation and correctly apply this to the General Ledger.