There shouldn't be an issue with your saved games when switching from OFW to CFW, just plug in your 1TB into your slim and have your FAT32 formatted flash drive ready with Rogero 4.40 1.03 and re-install it when it asks you to.
Keep in mind that some saved games are locked to the user, so not all of them would work when moved from 1 PS3 to another (or one user to another on the same PS3 for that matter)
CECHL 500GB: OFW 2.50 > OFW 2.76 > OFW 3.41 w/ dongle > OFW 3.55 > 3.55 kmeaw > Rebug 4.30.1 > Rebug 4.30.2
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Off to my summer vacation, might be AFK for a while... Happy Summer!