Finalizing the specs on a new Calfee Dragonfly. Group is going to be Dura Ace Di2, with the exception of an Ultegra 6870 GS rear derailuer.
The reason for the Ultegra RD is to get a larger rear cog capability. My question is whether to go with the K edge long cage modification, which takes the capacity from a 32 maximum rear cog to 36 max.
For context, we're going to set the bike up with 2 swappable gearing arrangements. Normal setup for flat to rolling terrain will be 53/39 with an 11-25. The mountain setup will be a 50/34 (interchangeable Lightning spider) with either an 11-32, or an 11-36. The 36 would be nice to have for really hard climbs, but we don't absolutely need it.
So the question becomes whether the long cage retrofit will hurt the crispness, speed,or accuracy of the shifting. If so, we'll skip the retrofit, if not we'll get it to add flexibility.