Right, so no swapping claws for bite. Understandable.
Until fourth level, you can only have three attacks. So, claw/claw/bite is the most efficient way to get those. The bite is a designed in interference so you cannot get four claw attacks at fourth level with the pounce ability. You have to wait until ninth level as a quadruped. At forth level, claw/claw/bite/gore is an efficient way to go.
Considering as a monk1/syn5 centaur form, you can do about 12d6+28 damage as all primary attacks on a pounce, why would you want to slow down to do flurry attacks. Actually, I could push that to about 16d6+32 if I went all damage with no defense. So, there is more than enough combat potential without doing a fully focused concentration on only claw attacks.
From a fluff standpoint, I'm just not a huge fan of the idea of having a bite attack, which is a definite part of my desire to swap it out. From mechanical standpoint, I'm going to be taking the Master of Many Styles, and focusing on applying style feats to my claw attacks (right now I'm thinking Dragon and Boar - I definitely like the flavor of Boar for this character), which does make for a significant difference between claws and other forms of natural attacks.
I had been thinking that, at Synthesist 4, I'd take limbs (arms) and claws anyway, to get the 4 claws, and just "eat" the extraneous, unusable bite (i.e. not use it at all), but if that's not going to be allowed, then I may give serious consideration to going biped. I really wanted pounce - great synergy with Dragon Style - but I really, really want those claw attacks.
Sorry; I don't mean to clutter up the General Discussion thread with musings on my build. I had thought about PM'ing you to discuss the build, SK, but this was on the heels of all my questions about Ni, and I didn't want to be greedy for Satin Knights Advice.
As to body form: I am not comfortable calling a gorilla like form a quadruped. That is a murky grey area. If you are wanting pounce and useful hands, a centaur form is the way to go. As the example above shows, it is quite strong after a just a few levels.
At the risk of being reactionary: this bothers me. It's fluff: I don't see how it affects you, since there's no mechanical, RAW benefit to how I conceptualize my eidolon-skin, so it bothers me that you would feel the need to voice a contrary opinion. The only issue I can see is that of functional hands, which is fair enough, although in my personal opinion, not allowing my PC to have functioning hands just because I want pounce, basically, is far too hard-line an interpretation of the system for my tastes, and I would hope that that wouldn't be a universal opinion. At the very least, I would hope we could acknowledge that, since this is indeed "a grey area," that any one opinion wouldn't be able to be made law.
Not trying to pick a fight; I always respect your opinion, SK. I just felt like that last comment was a bit to quick to dismiss my take on the character, without a lot to go on.