Just wanted to add a few notes to your build experience...
Steering limit pin:
The pin can be removed, but as you pointed out – no more dings in top tube from handle bars or down tube from brake caliper. The turn radius is limited, but after a few rides on the Serios , I felt like it had more than adequate turning ability for most races situations.
BB/ Di2 Access:
There is access thru the BB on the Serios.
The Praxis BB on the Serios is one of their earlier designs that has a aluminum sleeve that is inserted into a frame prior to inserting the bearing cups. In this version, the sleeve must be removed in order to run the wiring.
Praxis' newest Shimano BB for PF30/BB30 does have access ports thru the aluminum frame sleeve that will let a junction box through, making running of the Di2 wiring easier.
The hardest part is running wire thru the rear chain stay. However, since I did not have the specific Shimano wire routing tool from Park (http://www.parktool.com/...ble-routing-kit-ir-1), I created a makeshift wire pull utilizing a typical shifter cable, running it through the frames chain stay from the Rear derailleur to the BB.
Then I attached the wire to cable narp using a small piece of electrical tape. (in photo example below I used scotch tape to help illustrate).Then I slowly pulled wiring harness through chain stay to BB to connect to the junction box.
