I've played around with D-19 with a few conventional films like HP5 but not FP4. In determining development times as a starting point I derive a ratio between any conventional film with the known development times of a common developer like D-76/ID11 and D19 and then apply it to the film of interest with it's known development times of D-76/ID11. Another complicating factor is the ratios for stock vs. diluted developer times varies from film to film. I pretty much nailed down HP5 and D-19 at 6min 15sec and D19 1:1 at 9min 15sec. The 1:1 development could be scaled back by 15 or so seconds since it's a tad brighter compared to stock development but it's not significant. Without further bogging down in comparative details, the development times and ratio for FP4 and D76 is 8.5min/11min(1:1); The 1:1 dilute is 1.29 longer. Using my determined time for HP5/D19(6.25min) compared to D76(7.5min) which is .83. The FP4/D19 comes out at 7min and 9min(1:1). Again, it's a starting point.