No dear
@
Gieaux
you can't the only way to do so is downgrading with a hardware flasher.
If you are stuck in OFW as you say, downgrade buying E3 flasher.
There a bunch of good tutorials here to suit your needs and plus you can ask the community, but you have to open the PS3 in order to downgrade.
First if you are interested pass me the model number of your console.