Where should I mount the listed temp probes for the highest reading?
Your VPU would have the chance for the highest reading, depending on which card you have. followed by CPU, RAM and Case.
Bear in mind this is just a rough guide. Temps are different for every different chip and/or brand.
I think Coth was asking where to physically mount the thermocouples (probes) for each component... for the highest readings, the main rule of thumb is to get it as close to the heat source as possible.
CPU - mount the thermocouple as close as physically possible to the CPU die or heatspreader. (since heat rises, you may want to mount it on the top side).
GPU - push the thermocouple underneath the heatsink towards the processor core
RAM - if your Ram has a heatspreader, then push the thermocouple under the heatspreader between two chips. if your RAM doesn't have a heatspreader, then you could just tape it onto the top of one RAM sticks.
CASE - there's no easy answer for the case location. you'll probably have to experiment with that one. some areas of your case will not get good airflow and other areas will get very good airflow, neither extreme is a good indicator of your actual ambient case temp. if I were you I would use that sensor to read the HDD temps
For CPU, I have mounted mine on the underside of the heatsink, right next to the heatspreader. This would not give the highest possible reading, but its the highest without actually being in between the heatsink and the chip itself (which would increase my temps).
For CPU, same with GPU if there's space. Haven't really put one on that.
RAM - same as King Cody
Case - If you really want the ambient temp in the case, I'd say somewhere in the unused 5.25" bays. If you're gonna follow KingCody's suggestion, you'd stick it where it spins: in the middle of the spindle circle. There's where the HDDs are hottest.