Thank you so much everyone for posting this information about how the front brake cable can be routed through the fork!!! This was my only gripe with the P-Series, and I couldn't justify 2-3x the cost of getting the P5 just for this.

I had no idea expander plugs with cable holes existed, and I found about 8 different options. While there are many solid options out there, I didn't want to deal with any faff so I just got this sketchy one from Amazon you can see below. Looking at AliExpress there are actually 3-4 of these different designs, but considering this one is so similar to a basic expander, I figure it's probably the best of the worst options.




Anyway, I managed to install it just fine. I like how the cable route is angled, so the cable is easier to feed into the handlebar. I also got a cheap aluminum top cap I drilled a hole into. The top cap bolt that comes with the P-Series is terrible, that thing is rusting and paint flaking off.

I went out for a test ride today with this new cable routing + handlebars + extensions + levers + waxed chain and saw some immense aero improvements. Probably mostly from everything not related to the cable, but it's still a solid gain :D

Now my only gripe with this bike is how annoying the rear derailleur cable is to feed through from the BB flap to the rear hole. Why couldn't Cervelo just add a funnel or something to the end so it just goes through first time, instead requiring me to do bicycle yoga with one hand feeding the cable and another holding my phone's light through the hole to see where I'm poking. Maybe I should just get one of those temporary cable guides to save myself some hassle...