Finished the build today.
With my Tascam 70D putting out 46,5 to 47V and the Simple P48 made of 68kOhm resistor and 4,7uF cap I measured 8,2 to 8,7 V across the capsule (with some background noise).
I trusted Jules' instructable (thanks, Jules!) and omitted the shielding for the capsules. Nice, clean audio without electrical interference.
If anyone is interested: for the mics' bodies I used ultra cheap (~50 cents) lavaliers from aliexpress. But that's for a separate thread I guess?