Agfa says Delta 400, 20C, 1:50, 18 minutes at EI 250 for a gamma of 0.65. They also say:
Agitation: Small tanks – continuously for the first minute, and then tilt every 30 seconds. The film development times listed below are guidelines. Through variations in processing the result can be influenced according to requirements.
NOTE: all of the above times, for films and Rodinal developer, are suggesed starting times. For best results a test run should be made under individual conditions.
If you want to get closer to EI400 and keep the contrast down, you could try agitation only every 3rd to 5th minute, while prolonging the development time by 25%-50%. That gives extra time for the shadows to develop (higher effective film speed), and less agitation keeps the highlights from building too much density.
Either way, you'll need to test for your own circumstances.
Lee
"There ain't no sanity clause." - Chico Marx