Ok so my new bike has compact crank. For trainning rides I'm using 12-25, I have low gears that I want and don't really care that I go slower on the down hills. For racing thats another story. Is it possible to get 11-25 cassette? Another option is mix and match from two cassetes. Would using upper 3 cogs of a 12-25 cassete on a 11-23 cassette work? Looking at shimano site I would be loosing 19 cog.