Tried to post this on your blog but I get "Google sign in error":
[1] I agree with you about Hoyland. Well structured, clear and simple prose style. My recommended first read for those new to the period.
[2] The Arabs never developed any tradition of horse archery but the Turks, as steppe nomads, did. In the later period (post Conquest) you've got to remember there were a lot of Moslem Turks in the Eastern empire, and the Eastern armies, and the Abbasids took over from the East. Kennedy covers this in his "The army of the Caliphs" chapter 5: "The armies of Samara 833-70 - The coming of the Turks and the new model army".
Hope that helps?