A quick web search (duck duck go: at command set +class "HC-05") turned up a bit of docs (on slideshare) that mentions it. From what I read (not the whole thing) it looks like many of the parameters are in hex for many of the commands. The next entry in the document, for example shows that for "AT+IAC=<PARAM>" that the default value is 9e8b33.
So I'd try converting 99 to hex (63) and sending:
AT+CLASS=63
(Note: I'd've put in a link to the documentation, but as a new member here, I didn't want to run the risk of being marked a spambot due to having an offsite URL in a short reply.)
Hope that gets you going!
UPDATE: I just read the appendix in the above document, and it contains an appendix that appears to be a description of the class field. It says that it's a 32 bit field, and shows various tables describing what the bits mean in various instances. (It's rather more complex than I'd've thought, as there are about 6 pages containing nine tables covering subsections of the 32 bit number. Kind of interesting.)
Roboticus got a reaction from chicken in Anyone tried to use AT+CLASS= on the HC-05 Bluetooth module?