Where did you get the 500 foot above circuit that you mentioned in your earlier post?
Can't be sure, must have been in my ground class syllabus. I was certainly expected to know this when tested for legal knowledge.
As a matter of fact, several Belgian a/d's have explicited this "rule", EBHN for one example with the circuit at 700' and "integration" at 1200'. Several can't, however, like poor EBGB with its ATZ tucked in a forlorn corner of Brussels CTR and topped off at 1000'. Again: final info comes from authorative sources like the AIP, or, lacking that, from the a/d operator.