You probably have found this already but the few developers I have found times for are 7 mins. Rodinal 1+50 is 9 mins
I'd have thought but don't know that somewhere around the same times apply to DDX. Find other films and check those times in D76 or ID11 and compare with DDX. This will give a good idea how big a range of films have dev times close in both say ID11 and DDX.
It is then a question of extrapolating.
If you have a lot of this stuff to develop you can either risk say 7-8 mins in DDX and then alter accordingly or cut the film into two or three and risk the loss of three negs and develop one for 7-8 mins then alter for the other half or two thirds of the film.
The loss of three negs will get you very close to where you need to be
Best of luck