felt is going to lose a huge amount of sales because of the head tube issue. trek/parlee do it right. they offer the same frame with two different head tube lengths. most italian/belgian carbon frames all have tall head tubes. i don't think pinarello would redesign the dogma for millar
btw. the z series frame looks like a mtb frame. ugly.....
I know this is from 2010, but I still keep seeing the same whining about Felt's F Series needing TALLER head tubes. As SuperDave keeps repeating, Felt has different lines to address most riders' different fit needs. Don't get an F if it doesn't work for you - simple.
My experience with the F is the exact opposite of many others on this thread. I need a shorter head tube and a longer top tube - less stack, more reach. I've got a 51cm F series with the stem slammed (a 130mm no less), the seat push back past the max point, and still a minimal amount of seatpost showing. Compared to my previous bikes, I still need about a 140mm stem with negative rise so I could move my saddle forward 5mm, and lower my bars so I can match the fit on my other bikes. I've had 2 different fitters (1 BG & 1 Retul) look at my fit and both came up with the same fit for me. I just have really short legs and a really long torso. A Cannondale CAAD10 or Supersix is even worse as fit goes for me. The Felt F has one of the racier geomtries out there (fit-wise), and it still is too short and tall for me. I did the research (I tested Spec. Tarmac & Venge, CAAD10 & Supersix, Cervelo S5, Fuji Altamira & SST), and the F Series was as close too fitting me as I could get (I didn't test a Giant TCR in person, but on paper their geometry might fit me a bit better than the Felt, but it has a taller headtube so...). I am ordering a custom Landshark to address my fit issues.
Anyway, my point is different strokes for different folks/YMMV. Felt keep the F the way it is (although I wouldn't mind it if you made the top tube longer/increased reach).