There's a lot of bad info about dump valves, where they should be, and what they do.

To do the only thing they do, which is help prevent the turbo going in to the surge part of the map when you close the throttle, they should be as near to the compressor outlet as possible.

Rubber diaphragms etc dont like the many hundreds of degrees C that compressor outlet temps are though, so after the intercooler is often a more reliable bet with little disadvantage.

If you want to keep turbo response as fast as possible (and haven't got a AFM or something that requires a dump valve to operate correctly) the best position for the dump valve is in the dustbin or on ebay.

Turbos dont stall btw, the airflow from them does, but the turbos dont. If you watch a turbo RPM gauge they actually slow less with no DV fitted than they do with one fitted. Which is why you get chatter/surge, as the compressor goes to a far left part of the map where the airflow is almost zero but the turbo rpm is still high as fook.
A dump valve basically allows the compressor to keep flowing air and slows it down, which brings it back in to normal areas of the compressor map.

On that note, if you've got a DV that chatters THEN dumps, you may as well not have one at all, as the initial surge is the bit that will cause stress on the turbo to be honest.