I assume by softmod you mean exploit?
What "config" did you delete, if it was "Your System Configuration", thats why you lost your softmod. Just use an existing copy of uLaunchelf, and copy just the new boot.elf over the old one. I think uLaunchelf will try and read an old config, and I belive that it won't have too much trouble with it, although I could be wrong, but in any case it won't kill your exploit.
But just to be on the safe side copy the "Your system configuration" file to another memory card, and test that the exploit loads from there before attempting an upgrade.
Gaming Console: v7 PS2 Independence Exploit + 200gb Segate HDD
Development Console: v7 PS2 DMS4 Pro + EE_SIO Cable + 6gb HDD