Andy's tool failed with a arithmetic error (I will PM him). I was able to do a SSV3 mod manually. Check it out. Checksums are OK, but I agree it is high risk, I am puzzled by the 4 extra bytes after 1B that kills the tool I suppose.
M3N78-EM ver 0511 was tested working by 2 people. There wasn't feedback given for ver 0520 so it is possible that one doesn't work. Looking at 0520 I see it was modded SSV2 and there is a Dell SLIC at 60000, but there is also a fake SLIC in the 1B module which was there originally. Maybe the fake SLIC is being seen instead of the Dell SLIC. We can do a new mod. Don't flash from Windows though-- copy the bios to a usb flash drive and use afudos or the flash utility in bios setup.
You can use Everest to see if SLIC is already present. (There is always a chance!) But if it wasn't there or if it wasn't a valid SLIC then a bootloader would be the only option.