Geoffrey Crawley discussed using dilute DK50 in a series of eight articles on Developers in Dec/Jan 1960/61 in the British Journal of Photography.

The data was included in subsequent BJP Almanacs /Annuals. You need to make up an additional solution of approx 8.3% Sodium Metaborate (Kodalk). This is said to give "a useful balance of natural acutance, gradation and speed qualities with controlled contrast rise" Effectively this is 1+4 with additional alkali.

Dilute DK-50

Part A
Stock DK-50 (full strength)

Part B
Sodium Metaborate (Kodalk) 83.3gms (1oz)
Boiled Water to 1 litre (12oz)

To use:

2 Parts A - DK50
1 Part B
7 parts water

Development times: FP4 8-9 mins @ 20C, Pan-X 10-12 mins, Tri-X 13 mins.

Hope that helps

Ian