I have no experience with Efke PL 100, but I use Efke R100 (roll film in 120 format) and KB100 (35mm). I've also tried R50 and R25.
I expose R100 at EI 100, and develop in Rodinal 1+50 at 20 deg. Celsius, for 10:30 to 11:00 minutes, depending on lighting conditions (shorter time for contrasty scenes, longer time for "drab" lighting). The contrast also depends on agitation: I use 30 sec. agitation for the first half minute, and then 1 inversion and about 10 sec. agitation every minute after that.
For R50, my dev. time in Rodinal 1+50 is about 9 minutes, and for R25 about 7 minutes. Everything is shot at nominal EI - i.e. R100 at EI 100, R50 at EI 50, and R25 at EI 25.
The "Plane" shot in my gallery was done on R25, developed in Rodinal 1+50, at 6:30 minutes - in Jobo CPE 2 processor, which is the reason for shorter dev. time. Hand tank would have been 7 minutes. Shot at EI 25.

PS: presoak is obligatory! 5 minutes in Jobo processor, or 1-2 minutes in hand tank. The water comes out deep blue (or something like that, I'm relatively colour-blind )