Synthesist summoner questions regarding form and movement

[LucyG92]

So I'm a bit confused about how the Synthesist moves when merged with their Eidolon. Say you have an Eidolon which looks like a snake, so no limbs. When merged, can the Synthesist still walk around and wave their arms about? Can they attack with those arms even though the snake Eidolon couldn't? I realise they wouldn't be able to cast spells due to the specific point made about that (that's why I'm wondering about the other stuff).

On the other hand, if the Eidolon has multiple limbs that the Summoner doesn't have, like extra arms, presumably they can still be used? It's just this bit that sounds like it casts doubt:

Quote:

The synthesist wears the eidolon like translucent, living armor.

[Sah]

Think of it like piloting a mech. You are encased in the Eidolon, and by all outward appearances, you move only how the Eidolon could move. So with a serpentine base and no limbs, you'll just slither around, but with something like a multi limbed monstrosity, you can control those extra limbs because you are in control of the extra body.

Like a Gundam with wings, the pilot doesn't have wings, but has control of the entire mech.