The carbon strings, such as the Alliance are slippery little suckers. You may want to do an extra wrap on these strings when tying them to the block. On the high E, when using Carbon, I use four wraps and have not had them slip. The B and G I use 3 wraps and haven't had slipping. You should see the last wrap land near the hole on the tie block.
Strings by Mail sells many carbon string brands as singles, so you can experiment and find what you like, with relatively little expense. A lot of people just by a set that they like, and replace the G with an Alliance G.