Have not tried a 50/34 and 12/27 on the Sram Dual Drive kais01. Could be workable and might be a good solution. The other thing with SRAM DD was the weight. Compared to Capreo which was much lighter and the cassettes isn't really that expensive, I chose Capreo. Weight weenism won over. I also took the bike on overseas holidays and did not want to wrestle with the unfamiliar task of removing the rear wheel in the event of a puncture. Am more familiar with a normal derailleur system. The issues with friction and high cadence on the 9T, I don't really find an issue. Truthfully, I seldom use the 9T for extended periods or even the 10T. Fast cruising speed around 35/36kmh probably uses the 11 or 12 tooth only. Which is why I also concluded that it is not necessary to go above 108 gear inches. I won't be able to sustain above 43-45kmh for more than 3-5km drafting a group