Do both lights still work normally with their respective heads on? Or did the experiment damage one?
This should have been fine to do - many of the Fenix vendors will sell the L2D 2xAA tail and body as an option for the L1D. I don't think it should make a difference that the L1D is a Q5 and the L2D a regular CE model.
I hope I'm right because I may have suggested you try this