I used to use FP4 exclusively as I obtained it rather cheaply in bulk form. I would shoot it from 80 ASA through to 160 ASA and developed it as though it was 125 ASA (or box speed).
This was quite good and I remember the only difference was shadow detail certainly not being as good as it could have been at 160 ASA.
Once on a camping holiday in the middle of nowhere, I came upon this photographer who went out in the morning to shoot, returning around late breakfast time and disappearing into the big box on the back of his truck to develop his film; which was FP4. I found out he was exposing it at 200 ASA and developing it accordingly. I was unaware at that time (1969) that you could successfully expose FP4 at 200 ASA and get good negatives.
I tried exposing at 200 ASA but for whatever reason things weren’t too flash. I then found out you needed to extend the development to get pretty good results; I did. My results were better, time marched on I became better, as did my negatives.
Eventually FP4 was replaced with FP4+, by then I was using a Jobo and rotary processing. I was certainly a far better technical photographer by that time and still used FP4+ for virtually all of my photography. I could and did shoot from 80 ASA through to 160 ASA on a single roll and develop normally; living with the under and over exposure by adjusting in the darkroom.
Around 1990-1991 I was at the Ilford Australia head office, which was quite large then. I got speaking to one of their technicians who normally helped with our graphic arts requirements. He informed me that while you could get and do get good and extremely usable images doing what I was doing, I would possibly be better off by exposing at 200 ASA and developing for 200 ASA. This was with the then new FP4+ film, which was why we were talking about it.
I did do that and found that I certainly got better results by exposing at 200 ASA and developing for 200 ASA. I found 1+1 gave me the best results in D76, or at least results I preferred. I used FP4+ at 200 ASA until I discovered Fuji Neopan 400, which I have used since as my standard 135 format film, I’m just starting to run out, maybe about a year of that left.
I never warmed to HP5+ although many have, so I stuck with FP4+. I did when required push it to 400 ASA and used Microphen; about the only time I have used Ilford developer. That combination is alright, but I never went gaga over it.
To be more specific for your requests. I looked up some of my processing of 135 FP4+ that I developed in 2000-2001. Where I exposed it between 80 ASA through to 160 ASA on single rolls. Jobo 1540 tank (4 rolls of film) using 500ml of developing solution, rotary developing, D76 1+1 for a diffused enlarger head, 16’15” at 20ºC.
This was my standard time for that film, tank and developer with rotary developing, which worked quite well for me.
I still use FP4+ extensively in 4x5” sheet format, it is my favourite film for that format. I have, on only a handful of times, upped that film from my standard 100 ASA to 160 ASA or 200 ASA. I see in this format, things one doesn’t see that easily in 135 format. When I have exposed FP4+ at 200 ASA and developed accordingly, or as best as I can for each single sheet of film. It is and can be really good, but the reality is, it just doesn’t cut the mustard shadow detail wise, as rating HP5+ at 200 ASA. But nonetheless, at that 200 ASA exposure, it is pretty good.
4x5” sheet film is the only place I shoot HP5+.
What you are wishing to do, should work well.
Mick.