Bicycle Mechanics - New Cassette

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.
11,12,13,14,15,16,17,19,21,23
12,13,14,15,16,17,19,21,23,25
Thanks.

I don't get why. You have one tooth difference and it's a measley 10 gear inch difference on a 52 chainring from 12 to 11. Anyways to answer your question, the same query has been posted in the road cycling forum not too long ago.

I don't get why. You have one tooth difference and it's a measley 10 gear inch difference on a 52 chainring from 12 to 11. Anyways to answer your question, the same query has been posted in the road cycling forum not too long ago.
I have compact so it will be 50 up front. Anyway only thread I found was: Digging my 11-27 "custom" Dura-Ace cassette! So I'm guessing it kind of answers my question you can mix and match. Although I'm not sure how he kept the 19th cog. Since last three are connected together.

My experiment for now, 1st 5 of the 11-23, last 5 of the 12-25 (lost the 16). We shall see how it works on my next ride.

My experiment for now, 1st 5 of the 11-23, last 5 of the 12-25 (lost the 16). We shall see how it works on my next ride.
Kool, let me know how it will work out.

Funny, I've gone the exact opposite way. I have no use for a 12T so I customized a 12x27 9-speed Shimano cassette to 13x27. I got a 13T top cog salvaged from a used 13x25 9-speed cassette, discarded the original 12 and 13T cogs and added a 16T to the stack. The 16 is very useful and I now have exactly what I want.

Funny, I've gone the exact opposite way. I have no use for a 12T so I customized a 12x27 9-speed Shimano cassette to 13x27. I got a 13T top cog salvaged from a used 13x25 9-speed cassette, discarded the original 12 and 13T cogs and added a 16T to the stack. The 16 is very useful and I now have exactly what I want.

Good idea. All of my cassettes start with a 13 and include the 16, Shimano and Campy.

I built a 11x25 with two shimano cassettes, or you can go to xxcycle.com and pull up miche cassettes. you can custom build a cassette for around 50 bucks.