Q before back vowels

On pg. 27 fn. 18 I mention that Q was used to spell /k/ before /u/ and the spelling PEQVNIA is the preferred one in official documents up until the time of Cicero. I should also have noted that Q for /k/ and even /g/ is found before /o/ in some archaic documents, e.g. LVQORCOS (ILLRP 767, Praeneste) = Λυκοῦργος, EQO (ILLRP 739, 744) = ego. There are also instances of Q before syllabic u from as late as the 1st century CE, e.g. CONTIQUERE (CIL 4.4191 etc., Pompeii, a citation of Verg. Aen. 2.1). This use of Q before rounded vowels other than u presumably cannot be derived directly from Etruscan since Etruscan only had /u/. The early Latin practice may have been an extrapolation from Etruscan or an approximation to Greek practice where qoppa was used before back rounded vowels.