Safety wise, shouldn't be a problem, if I am remembering Diesel Test correctly. However, depending on your age, condition etc. it might just be a waste of one of the supplements.
If you are going to stack, I would advise staggering the stack (Maybe 2 weeks Diesel Test, then add in the IGF-2, or vice versa.) This will allow you to see how the Diesel and/or IGF-2 Works, then how they work synergistically.
I have a strong feeling the IGF-2 would be all you need to see some results.