Beavertails....
Hi,
I think (its hard work but I try
) that the beavertail is to protect the cocking rod. It also encourages the mask not to hang sooo tightly to the bolt, which might hit it craking the lense (sounds far-fetched I suppose, but a good wack in the face is not what you want really anyway).
I don't think rear cocking is better in itself except that it reduces the profile. After all the direction of cocking is backwards not sideways anyway.
Maybe I'm just spouting BS, but hope that is of some help,
Maybe someone who knows will post in a bit
Richard