The Surly Pacer is a steel road bike designed for long, all-day rides. In my size (54cm), it has almost the same stack & reach geometry as the Cervelo. IOW, it's basically the same fit. So I bought a Pacer and added fenders, to have a the same ride for winter training and more casual long rides.
The Pacer has one design flaw for long rides though: the rear brake cable runs along the top of the top tube, most of it exposed, which prevents you from using a Bento Box-style top tube bag. On long rides, I like to small amounts relatively regularly, and a top tube bag makes that much easier than jersey pockets. I like the eoGear top tube bags.
So I designed a shim using Tinkercad and printed it on a 3D printer locally using 3D Hubs. The shim rests on the top tube and protects the exposed cable (rear) and cable housing (front). The bag will rest on the shim, instead of directly on the top tube. The design is available here, if you want to print one or modify it.
Updates: Here is the shim (unpainted) with the top tube bag.
And this is the shim painted and affixed with thin two-sided tape. Works like a charm.
A coat of flat black paint makes the shim disappear.
