If you are a US operator then FARs will apply but then you should hold a dispatch licence and therefore you ought not to be asking this question. If you have a JAR AOC then you should consult JAR-OPS1 AMC OPS 1.255 (2) and your company OM Part A (Sec 8). This will refer to the DPP Decision Point Procedure. (An interesting point is that FAA licenced Dispatchers will know all about this whereas a JAR-OPS 1 Ops officer, on the whole, will be ignorant of this. Is this right?) You will need to be compliant with JAR 1.205 and 1.210, does your company have an Ops Procedures Manual? The pros of this procedure is that it can extend range v payload or reduce fuel uplift and consumption where all of the safety factors have been considered. The cons are that highly trained staff are required to administer this yet JAR is very wooley with regards to these training requirements when compared with FARs, a good flight planning system and a robust method of flight watch and communication with your aircraft if flight crew workload is not to be over burdened.
Rgds
EM