huš-/huv- and RUKI

An observation from study of Old Persian:

• Learn the RUKI rule. In Indo-European languages, most things ended in -os/-us. Greek and Latin preserved a lot of that. However, in Iranian languages, you see most things ending in -ah (where the h isn't written.) Why? The RUKI rule. Generally, between Iranian and other IE languages, s becomes h (ie. sam-/ham-, soma/haoma, ) except after R, U, K (and X), and I, where it became š. Hence, Dārayavauš versus Darius.
  
• The word for "Good." It appears that the enclitic hu- meaning "good", is related to Greek eu. Interestingly enough, depending on the word it modifies, hu- can either end in a v (before vowels), nothing (before consonants), or a š before an h (via RUKI) -- this results in huš-/huv-.
  
• H -> X. Judging from Greek, Elamite and Akkadian transliterations, as well as development into Middle Persian, it appears that initial h especially before u was a very hard h, possibly pharyngeal, and eventually became x. So with above, what we'd see in huš-/huv would become xuš-/xuv- and eventually xuš/xub. This jives with New Persian, as both of those words mean "good," but with slightly different connotations.