I just realised that you have suggested IDs in the description under the titles of the photos.
R. arnoldi isn't found in Sabah at all, although it is further south in Borneo (in Sarawak, and I guess southern Kalimantan). It is quite a bit larger than R. keithii as well.
Regarding smell, the species differ in how odiferous they are (so I have read). Some species are stinky and others not.
Oh, interesting! I didn't knew that are some stinky species while others are not!
Also could be taken in account that in some other flowers that imitate carrion (big to enormous, purplish red, and with rotten flesh stink), such as Dracunculus vulgaris or Stapelia, the smell is present only during the first day of opening, from this to the decaying of the flower few days later, it's not smelly. I guess that this is a strategy for do the pollination in time.
