I have used that cheap stuff for mounting Golden Orb to video cards, coolers to MOSFETS, and heatsinks to chipsets. I can say that this stuff holds and holds well. As for thermal properties, I have not really had a problem at all. Also when it comes to RAM chips, the thermal properties are not going to matter that much because they heat up gracefully, unlike CPUs that go 0-1000C in 2 seconds
If you are really worried about thermal properties, get the cheap stuff, make a very small batch, dab a drop of the adheasive on the corners of the chips and put AS3 everywhere else. The adheasive will hold the heatsink there and the AS3 will move the heat. I used this trick when mounting a Blorb on my nForce2 chipset; dabed 2 drops of epoxy on 2 corners of the chip and used AS3 in the middle. That HSF is NOT going to move and that chip does not even get warm to the touch, even with a Vmod and running @ 210FSB.