With the adjustable seat post that Cervelo advertises allowing the effective seat tube angle to adjust from 75 - 78 degrees on I believe all of their tri bikes, wouldn’t that be the equivalent of modifying a road bike to be ridden in the forward position? And conversely, if the bike is built for the forward position would that not make the slacker position inefficient? I was just curious, most people on this forum are not crazy about modifying road bikes, but love the Cervelos.
Thanks
BUMP
Is this a stupid question, or is it being ignored?
???
Most road bikes are built with seat tube angles (STA) between 72 - 74 degrees, so modifying it with a forward seatpost, will shorten the top tube between 2 to 4 cm’s, possibly rotating the center of gravity into an unstable position. Cervelo’s are purportedly designed to allow for this CG travel between 75 - 78 degree STA. It’s pretty hard to design for a CG travel of 72 - 78 degree STA. So, if you want to ride a Cervelo tri-bike slacker than 75 degrees, get a Soloist. As for inefficiencies, I believe that’s a matter of you and how much time you spend training.
Thanks 
.
best explanation i’ve read: