Stupid question 5.1 -> 5.01, JB -> 5.1?

[Scatabrain]

On 5.01 and JB works great. Iph 4s.

Had to lose app save data in process.

Is there a way to access app save data from 5.1 backup (local not ickoud) to get the save data back for some apps?

I can live with losing all but Memento. I forgot to export the posts before downgrading.

I am assuming upgrading to 5.1 will destroy JB.

Considering backing up, upgrading, saving data, downgrading, JB etc. hoping there is a hack to avoid this.

Thanks in advance for any help.

Scatabrain