How to configure the battery percentage at which the mac will hibernate
I had a similar problm, and found that there was no ready-made solution to force the computer to sleep at a different battery percentage (eg. go into "Safe Sleep" at 5% instead of 1%).

The (lame) workaround I ended up using was using SlimBattery Monitor to issue a pop-up warning at a custom battery percentage (for me it was 20%), at which point I must close my laptop/manually tell it to sleep, until I can get it on AC power.

It seems you would have to write your own applescript to make the computer sleep if the battery is too low, and add a LaunchAgent to have it repeatedly run the script to check the battery power.  Annoying enough that I didn't venture down that path.  I was surprised none of the many battery-monitoring programs had this funcitonality (I may have just missed the one that does).