Data transferring from any firmware to any firmware will not alter the firmware of either ps3. Thousands can confirm this.

You will need to have your actual PSN account on your 3.55, ignore this part if you already do.
You will need to install 3.55 rebug, You must login or register to view this content. , then download, install, and run the spoof from the same website.
Now you will be able to data transfer from 3.72+ to 3.55 to add your PSN account to your 3.55

---

Now you can CFW save hack any game by just swapping files with FTP/File Manager.

so how do u actually do the data transfer what stuff do u transfer.

Not certain what you're asking, but You must login or register to view this content. should answer all questions.

but wont the one with ofw get overwritten by the rebug one when i data transfer??

Yes, that's the point.

but wont i lose my stuff on my ofw