I really like the idea that Elvish temporal and spatial relations are reversed from English, and therefore favor Q. epe "before of space, after of time" and nó "after of space, before of time". But that is just cherry picking from the available options.

+Paul Strack I belive we could still use those, as well as the ones above. In my understanding, Tolkien's final decisions were to use them exactly as you said, until the roots in PE22. I still view them valid since the idea is woven into Eä [VT49/12]. And honestly, only thing that encourages me to employ these newly found roots is the ambiguity of nó in itself, opposing its meaning over and over again. From Early √NOWO to Merin Sentence and everything in between. I can't wait for +Александр Запрягаев's approach to this problem.

What are the theoretical Old Sindarin forms? ;)

+ܤܡܝ ܦܠܕܢܝܘܤ Are they incorrect?
Faw: pʰā > pʰǭ > ɸǭ > ɸau > fau
Cad: kata > kat > kad
Haw: kʰjā > kʰā > kʰǭ > xǭ > xau > hau
Pad: pata > pat > pad

There's the issue of "long final vowels were shorthened -> short final vowels vanished" with √PHĀ and √KHYĀ but that would leave me with just consonants. All the examples I could find (on 'ā>a>ø') have at least two syllables, and we have baw from √BĀ/ABA as a single syllable.

+Ekin Gören As a temporal solution, maybe. But everyone who hopes to find PE22 LVS1 to be a 'final' solution, pay attention to PE22:167, 168 LVS14…

"As a temporal solution" - I see what you did there...+Александр Запрягаев

+Александр Запрягаев I assume you're refering to these:
EPE, after of time, or[?] after of place. AWA, before of time, OPO, before of place.(p. 167)

And the rest from the next page:
{ epe , before of time.} { awa .}
ō { hō , from. [?being] {near, behind, past[?] >>} (...)
epe, 'after' {before} of time. after, behind of place.
awa, before, ago of time. opo, before, ahead, in front of place.
auta, ago. autas, a former occur[rence]. (p. 168)

What a mess... Thanks for the heads-up.

+Ekin Gören
I asked also because I was keen on knowing whether there was any case ending (*-se or *-da) present in the proto-stages.