Yep, they are floating around PS3 Dev circles and apparently 3.61 also is incoming, but short of knowing someone with a Debug PS3 to test them you may have to wait until someone leaks them publicly for a confirmation.
I think I found the Debug Firmware 3.50/ 3.55 and 3.60 but I have no way to test.
I think I may be able to test bud, but I will unpack them 1st and have a look, upload them with a md5 code and tell me on here, or the other point of contact where, its up to you and I'll let ya know, and any others if there interested.
I have not had a chance to look at this fully yet ConsoleDev but it does show as a 3.50 pup, but its not a 3.50 ofw looking at the signature of it. There are a number of file size differences that show the update pup you uploaded ConsoleDev is missing something? but I've not found what yet
Would you upload the 3.55 bud, so when I do have the time to look at them deeper over the next day or so, I can do both at the same time