I have an HP 4952A as well and want to start playing with its brains but I have a few questions.
How are you getting your custom code onto the machine? I do not have a floppy drive so I am not sure what I will need for a mondern computer. USB FDD, FDD Emulator?
LIF_Utils says the disks are:
lifversion: 010708
Volume : HP4952
Tracks: 77 Surfaces: 2 Blocks per Track: 16 Total size: 2464 Blocks, 630784 Bytes
Directory start : 2 (0/0/3) end : 11 (0/0/12)
User data start : 12 (0/0/13) end : 448 (14/0/1)
EXTD_ASYNC ?(C403) 22784/22784
COPYDISC ?(C403) 12544/12544
DEMO_DATA ?(C402) 41216/41216
TERM ?(C403) 22784/22784
IPARS_MEC ?(C403) 12544/12544
5 files (80 max), last block used: 448 of 2464
I have been able to pull off programs and open them in ghex. I see the structure your /lib/header.asm and similar files are refering too. I assume you destructed these programs to figure out the required file structure. I do not see anything on the hackaday.io page on how you actually achieved figuring this out. I assume dumping the ROM's and looking at all OUT commands then manually poking them?
Anyways, If you have some time can you summerise HOW you got to where you are and I will hopefully be able to help out! My neck of the woods as no computer clubs so it's slow going alone.