You have most certainly experienced trouble because of the "adding too much memory" bug in ACAtune. The heat issue, which is only present on a few cards, means random crashes on all kinds of occasions.
The test with the tiny cooler was successful: The A1200 with ACA1231 and the over-voltage power supply was still running it's endless LHA loop when I came into the shop this morning (note that this particular ACA1231 was failing without the cooler after about half an hour). I will describe the whole test procedure later today. The short version is: Since we don't know which card really requires a cooler, every customer will get another shipment from Vesalia with a free cooler and mounting equipment.