Own work
The base image used for the eastern borders was the "Ibraahim Muxamed" image sourced from page 76 of Taariikhda Soomaaliya depicted besides "Other Versions" below. Ibraahim Muxamed's borders are based upon the 1904 Illig treaty borders, which in this file is juxtaposed upon the proclaimed western Dervish borders.
Information for the western border is derived from the 1908 Dervish proclaimed border as stated in page 151 in Taariikhdii daraawiishta iyo Sayid Maxamed Cabdulle Xasan, Jaamac Cumar Ciise, 1976. The page depicts Buuhoodle, Badwein, Jidbali and the Warsangeli-Isaaq border as Dervish proclaimed territory, particularly in the following excerpt: "remove your party from Bohotle and also remove the horses from Badwein ... call back your spies from Jidbali, ... let me settle between the Isak and the Warsangeli" (accessible link)
The withdrawal from these positions was acquiesced on 15th March 1910 per the following source "He recommended that withdrawal be carried out on 15 March 1910, and this, of course, was approved" (Roy Irons, 2013)

The bottom shading (light/dark) represents the Halin, Hudin (Hudun), Tifafleh, and Danot (also called Docmo & Damot), borders from the Illig treaty circa 1904, shadings representing chronological progression, per page 90, of Roy Irons 2013 book "Betrayal and Redemption":

to the wells in the Nugal 'of Halin, and from these to those of Hudin, and from Hudin to Tifafleh, and from Tifafleh to Danot