If you are using existing holes, then the risk is minimal.  I have 4 of these Av16 Drillbit boards, which are stacked with the heatsink on top.  So far I did not have any separation issues and they are working quite reliably.  These are significantly less efficient than the older bitfury based boards and require plenty of cooling.  I'm using 12 cm fans in push-pull from the sides, blowing air through the fins and also some old HDD cooler dual fans on top of each heatsink.  This keeps it at a reasonable temp of about 47 deg C.  Overcloocked to Av16:int:750:1:1000 they produce about 88 GH/s altogether.

Cheers