I think the flashpoint is not important. VG boils at 290C (554F),PG boils at 188.2C (370.8F)
http://www.e-liq.com/information/e-liquid-bases
Vape pens boil the e-juice, thus likely to be hot enough even for non-decarbed oil. So the problems are in getting the right concentration. Also for your skunkfarmresearch link:
At saturation, Glycerin only hold as 33% as much cannabis oil as the same volume of ethyl (grain) alcohol, so about three times more is required per dose.
To reach maximum saturation however, requires processing more than one batch of fresh material through the glycerin, because as the saturation level increases, the glycerin becomes less aggressive as a solvent and the partially dissolved cannabis boundary layer interface with the solvent is also no longer at full strength and as reactive.
This is also very important I believe:
Keeping the boundary layer removed:
The boundary layer is the layer of partially reacted resin and dilute solvent that forms on the surface of the resin after the initial aggressive dissolution by the solvent. The solvent at that point is dilute, as is the resin concentration, so that the reaction slows or grinds to a halt.
To keep the reaction operating at a reasonable rate, we need to periodically or continuously remove that boundary layer, and there are four methods that I will present here.
The first is to stir. Simply stir gently and thoroughly with a wooden spoon
The second is to shake. Simply shake a jar of glycerin and plant material by hand regularly. A paint shaker would also work for this application.
The third is to tumble. Placing the jar of glycerin and plant material in a rock or photo film tumbler will keep the boundaries fresh. It is an effective and gentle way to speed up the process.
The forth is vibration. Placing jar of glycerin and plant material in a vibratory cartridge case cleaner, or other form of vibration, creates more shear energy that tumbling and will dissolve the material the fastest of any method we have tried thus far.
When I have material to use, I'm going to test cooking it in high temperature oil bath @ 250F for 30 minutes. It keeps it below the boiling point, yet at a better absorption temperature, which is also perfect for decarbing, both time and temperature wise.
I suspect though, it may best best to cook in 100% PG, then cut with VG that has cooked MJ in it.
I may invest in an ultrasonic jewlery cleaner also. Saw them for $30 in ebay.