Pretty sure Serotta and Klein made tri bikes with angles around the 80 degree mark

Klein may have in the past but didn't in 2007.

Serotta has a custom (CXII)

You slide your TF up to 80degrees I'd think iit would have pretty twitchy handling, lots of weight out toward the front, but to each their own

No, - wasn't bad on my TitanFlex 650c medium. I had a fork with a 43mm rake, a long top-tube (certain frames are longer than others) and a decent stem... wasn't be bad at all.

I hear this a lot about TitanFlex and I think the reason is that people run forks with short rakes.

The Yaqui Ocotillo and Manzanita are available in 78 degree configurations.
http://www.yaquiusa.com/

Since when does the Zaero have a round seat tube?



A custom version?

I have edited my post. I should clarify. I am looking for a round seat-post insert.

The Zaero has a round seatpost insert.

The reason why I am looking for this configuration is because it leave the option of using a forward seat-post (giving a very forward position - this is the goal).

I currently ride a Cervelo P2C and it just isn't steep enough...

My Yaqui Mariola has a round, 27.2 seatpost and seat tube of 81.5 degrees. In the four years I have had it I have gone forward more and back more and ended up pretty much where Ves designed it to be ridden. And contrary to an earlier post-er's opinion, handling is a function of design, not riding forward. Ves's bikes handle well when ridden steep because he knows what he is doing.
Chad

yaquiusa.com

Is that a custom Yaqui Mariola or is that stock? If stock, then what year?

The bike was stock DE (for Dan Empfield) Geometry. Ves offers four different geometries in a variety of sizes, so his bikes are effectively custom. If you are really a mutant and need custom it is something like an extra $200, but I doubt there are very many people who actually need this.
Chad