Regarding head tube, our 2013 Tetra was the first Calfee off the line to use the ENVE 2.0 tapered (1.125" (1 1/8") upper / 1.5" lower) fork. It has a straight 44mm head tube. The bulges you see on the lower portion are simply to provide for the shifter cable routing and a better cosmetic interface with the lower 1.5" headset piece. It is otherwise a straight 44mm head tube.
The Chris King InSet7 GripLock NoThreadSet Headset takes care of the taper conversion without any fuss or muss.
Info and photos posted here:
http://www.bikeforums.net/showthread...highlight=2013
Note, we have an optional 2cm head tube extension on this frame. Our current setup has my captain's stem installed with no spacers below the stem, right on the top of the headset for a perfect custom fit. After a season of racing singles, I was able to re-find my optimal lowest positioning and then removed the initial spacers we started out with on this 2013 tandem.
I am in the midst of some big upgrade changes (Di2, same-side belt drive, regular/single SL-K Light cranks, compact chainrings, etc) and will eventually post those photo updates to the forum.
---
Regarding disc fork selection, checkout Mickey Lyon's photo album on Facebook:
Calfee Carbon Fiber Travel Tandem with Rohloff Speedhub and Gates
https://www.facebook.com/ChoprDoctr/...4163724&type=3
and here:
Photos from Mickey Lyon's post in Calfee Owners
https://www.facebook.com/photo.php?f...e=1&permPage=1
They have ridden this setup on trails (as seen above), and many trips abroad. The disc fork appears to be a Wound-Up, with plenty of clearance for those big knobby tires he sometimes uses. It may not be the most svelte setup, but has proven to be very strong and durable. Since Calfee is not currently offering this fork on their list, it may be obsolete at this time.
That S&S tandem, with Rohloff, etc has a total weight near 40lbs, may be one of the heavier Calfee's out there.
Also this one built in a similar way:
https://picasaweb.google.com/1100502...43712381077426