Perfect Subjuntive Active

[GVR2]

In M&F (Page 328) the second person forms of perfect subjunctive active do not have a macron on the last i; nor do the first person plurals.

In Wheelock, however, they have (Page 453).

Which is correct? Thank you.

[Twpsyn]

Allen & Greenough give it short. However, I believe the quantity varied, especially in poetry: for example, in Catullus 5, line 10:

Dein, cum milia multa fecerimus

fecerimus has long i.

[GVR2]

Thank you.

[timeodanaos]

According to Sihler, §543,3, the latin perfect subjunctive is formed from *is-ī. With normal sound changes, this makes -erī-. Because of the likeness to the future perfect, the final i loses its quantity, though; except among early poets - and seldom seen metri causa in later poetry, and almost exclusively in the first and second person plural.