GUNGER,
I guess I don't understand your question. according to our company
(jar ops) you have to have enough to fly to dest. then alt and then hold for 30 minutes. so what you have at your destination depends on how far the alt is. Generally 30 min at alt is 1200kgs. However we use LIDO and the calcultations vary a bit from time to time. Another minimum we use, in case we burn more fuel to fly to dest and then to alt is to arrive at least with min reserve ( the 30 minutes) + 15 minutes. In case of arriving with less than that amount it is strongly recommended to divert enroute (goes back to the little jar ops rule that you don't have to have an alternate as other conditions are met but then you have to raise your final reserve fuel to 45 minutes) So that amount would be +-1800kgs.
As your question:arrive overhead, what do you mean? over the IAF. That would depend on how long it takes to complete the app. But still to have the final reserve + alt, or final at alt. This is KLM, there is no specific number, only a specific time expressed in fuel.
As BOAC ( I think) said the final min (30 minutes) is not enough to satisfy the minimum for operation of the ELEC HYD pumps. I have never been in that situation though. Brings me to a question (BOAC) would you in fact turn those pumps off? The question has come once in a while and the opinions vary.
Greetings