One of the most interesting and exciting aspects of establishing a NeoQuenya consensus is, to me, to determine which affixes attested in the Quenya corpus can be considered productive in the later Quneya stages and could be considered "safe" for use. PE22 has provided a lot of strong material with regards to that, especially the participial and verbal adjectival systems. It prompted me to start a sheet of PQ roots, their Quenya verbal derivations, the attested, and the potential verbal adjectives, frequentatives etc. of them, and the potential neologue glosses we could assign to them.
OS. [z] vanished before [d] lengthening preceding vowel; [Vzd] > [V̄d]
In Sindarin and Noldorin, [z] disappeared before the voiced stop [d], modifying the preceding vowel, though the exact phonetic rules evolved between the conceptual stages of the language. For Sindarin, this change is described in a couple places within notes on the Outline of Phonology [OP2] from around 1950:
OS. long final vowels were shortened; [-SV̄] > [-SV̆]
Primitive Elvish words often ended in long vowels, but in (Old) Sindarin these vowel were shortened in polysyllables, and later still, these short final vowels vanished. The evidence for these sound changes is so ubiquitous that it is not a question of whether these changes occurred, but when.