Please help: FP4+, ID11 and BTZS tubes (N and N+1.5)

[Craig Tuffin]

I'm so desperately rushed and have 6 sheets of FP4+ 4x5 to develop to do a few of 8x10 family enlargements for visitors for Christmas. I intend to do my film speed and developing time tests but don't have time to do it before they arrive.
The film was shot at 100ASA. Can anyone give me their successful developing times for stock solution and 1:1 for ID11/D76 at 68 degrees...Ilford quote 8 mins 30 sec for stock and 11 min for 1:1 but a friend of mine emailed and says it's closer to 10mins for stock
I also shot some with my highlights at zone 6.5 and was wondering what then would be the N+1.5 for that??? Is it 50% more time for each stop, therefore 75% longer developing in stock solution?
I know I have to do my tests to be spot on but I'd really appreciate your suggestions in the meantime.

Cheers

[Bjorn Nilsson]

This time really depends upon what you need for "normal". The first thing that usually varies is what light source do you have in your enlarger: condensed or cold light.
For an "N", 11 minutes shoud be in the ballpark for coldlight but 9.5 for condensed.
N+1.5 usually needs around 40% more time than the N, but again ... "ballpark".

I recon that you've used the BTZS tubes before and if so, you have got an idea of how much the constant agitation affects your dev.times. (I know that this varies from film to film, dev. to dev. etc. but FP4 is quite a "normal" film with "normal" reactions.)

//Björn