For the two or three people out there that have used a tri-bike with bar end shifters, throw them away and replace them with Vision Metron bar end shifters.
Cost is about $200, cheaper than the R2C shifters and considerably less than the Di2. The idea is that you squeeze them to move the gears one way, and press down with your thumb to move the gears the other way. Perfectly, and precisely.
What this means is that to go from small ring to big ring you squeeze (like a break), and the chain slips effortlessly into place. For the rear derailleur, a full squeeze will actually drop three gears, so essentially two or three squeezes will take you from hardest to easiest.
I put them on a few weeks ago for indoor training and had it outside for the first time this weekend. The idea of using tradition bar end shifters seems like archaic technology in comparison. Like those old road bikes with the shifters on the top tube.
When approaching a steep climb, it takes a couple squeezes with the right hand, and then press the left thumb to be into the easiest gear. When you reach the top, easily squeeze the left to bring your chain up into the big ring, and press a couple times with your right thumb as you accelerate.
It’s hard to describe how easy it is to get from small ring to big, compared to having to pull back on the traditional bar-end shifters–especially while staying aero. For me this has always been the biggest drawback of tri-bikes. Even on my road bike that process of getting from small ring to big involved a lot of work to get the integrated shifters to move far enough, while at the same time trying not to press on the front break.
If you’re serious about racing this summer, I strongly suggest you try these out. The Felt B12 has them stock.