Miguel:
>>> It's also attested in Old Polish. It's attested in Modern
>>> Polish, if you count ja biorę, oni biorą...
>>
>>That's different, I think.
>
> How is it different? What I'm saying is that
> "a.p.c-stressed" endings were lengthened (if not already
> long), and that "a.p.c-unstressed" endings were shortened
> (if not already short). Biorę :: biorą is exactly that.
No. This is the same thing wee see in archaic Croatian ve``lju - ve`le:.
The length in the 3rd person pl. (always there!) is due to a former *-t6
which was there, thus *be``roN > biorę (the length is shortened in final
open syllable), but *bero~Nt6 > biorą (the length from the neo-acute is
preserved and then the final *-t6 drops of). The place of the accent is
different, but there is no need for "lengthening" of the 3rd person
plural. It was already long. These examples are perfectly explainable
without your theory as well.
Besides, your theory is not really convincing. In Čakavian, there is only
živete``, roni:te``, pečemo`` etc. There is no **-te:, *-mo: anywhere. And
there is no convincing analogy there since a. p. b does not have final
accent in those forms. There is no *-té, *-mé in Czech as well.
Mate