I find it very good that the speed is not too fast
I think you may be confusing speed and length. R0 and R1 run at 15 or 20 minutes per day (4 or 3 game months per real life day), which is as fast as or faster than most other worlds. They run for significantly longer between resets, however.
If you're looking for slower (but also shorter) worlds due to time constraints, I suggest looking at the 30-minute-per-day worlds like R3 or R4. These run for about 7-8 months instead of 5 months for most 20-minute worlds. But R3 and R4 run for only 40 years game time (and will most likely be 30 years after they reset), so I'd stick with R1 if you want to take an airline all the way from the 50s through the modern era (but it's not a "slow" world).
In other words, R0/R1 are fast and long, while R3/R4 are slower but shorter than R0/R1.
Sorry if that sounds confusing.