Germanic P>+voice after u

In Germanic p>b after u and before any vowel. This is very early
and distinguishes between p and pY (as I've described before). For
example
*kaupos > OCS kupU; *kaubos > *xaupaz > E heap.

Since I've already said that both f and v existed in PIE and in most
languages f>s and v>w in most positions it follows that if f>v as p>b
in Germanic there will be a correspondence of Ger. w with non-Ger. s:

*mufí:x 'fly' > Lat. musca; Greek mui^a; *muví:x > *muwi: / *muwy+