I found the solution! First thing you must know, there is finally a little, very little gap between the underside and the adaptor PCB ( I found out looking at the sky with the device perpendicular to me shoulders ) but no way you can even apply the thin thermal pad ( adaptor comes with one thin and one a bit thicker ) because doing so makes it impossible for you to screw all the way down the M.2 on its standoff without breaking it. No way to put it on top either ( this is on design ), it goes underneath - only - if you have a one sided M.2.If you put it on top the heatsink of the adaptor will be pushing on your M.2 enough for the NAND modules underneath to touch PCB.
Now, I have applied the thin thermal pad on top and nothing on the underside. This is the best way to do it: good thermal transfer on top and since the NAND modules are anyway very close to the copper bands on PCB, it does pretty well on that side too.
Now one last thing, the stickers on any M.2 drive are not electrically conductive so if for any reason ( thermal expansion... ) the NAND blocs are coming in contact with PCB there should be no problem. More, since this drive will not be my system one it will most probably not generate a lot of heat.
O.K. guys, hope this could help other members some given time,see you all!
:-P