I can confirm that this works. I just did this upgrade.
I used a 3mm thick mk3 alum heatbed and a 3mm tempered glass. this raised my bed several mm, so I had to adjust the build plate homing tab height. I just used a bit of aluminum tape to extend the tab around 7mm.also, you need clamp the glass to the bed somehow, I am currently designing it in 123d design and will upload to thingiverse soon. in the meantime, I just bent some pci slot fill plates and it seems to work fine. I put a little glue under the glass to help hold it.
When doing this upgrade, remember to disconnect and leave disconnected the blue wires that connect to the back corners of the build plate. since the heat plate is aluminum, it could short out the motherboard if any voltage leaks through. so tape the blue wires down.
one issue though, sometime I get a 010 error because it takes longer for 130watt heater to heat up that much mass, it will get to 80C and then timeout, so I cancel the job at 70C, then restart it and walk away. perfect prints, no hotspots. no weak glass.