STBC02 Float voltage below 4.2v ?

Hi.

I would like to set a battery float voltage to 4.1v (to extend the life of the battery). Looking at the datasheet for the li-ion battery charger STBC02, it looks like this can be adjusted but 4.2v seems to be the min value (equation 3 on page 18).

Am I missing something, surely it would be a good feature to allow lower float voltages?

Thanks

Phil