Bingo! found this on Alex Berzin's site:http://www.berzinarchives.com/web/en/archives/approaching_buddhism/teachers/lineage_masters/biography_nagarjuna.html
which calls them the Six Collections of Reasoning (Rigs-tshogs drug)
simply calls it
These treatises, known as the Collection of Reasonings, include the famous Fundamental Wisdom of the Middle Way, and its four limbs: Sixty Reasonings, Seventy Emptinesses, Finely Woven, and Refutation of Objections.
which omits the Ratnavali, which of course makes five.
Great! Thanks to that old Master, Alex Berzin! (A thoroughly under-rated teacher in my opinion.)
The name he uses, "Six Collections of Reasoning" - if the six --> five, is pretty much how I read the Chinese.
Curious too, that his translation for the Vigraha is identical to mine!
But I'm wondering about "Finely Woven" as "Mahāyāna Refutation of Existence Treatise (大乘破有論 *Bhāvasaṃkranti Śāstra)". Names of texts often differ a fair bit, (eg. Mulamadhyamaka = Prajnamula), so I'll have to double check.