I would develop normally in Ilford Perceptol which is a speed-reducing, ultra fine grain developer. Tri-X 400 in Perceptol is rated at ISO 200 for normal contrast (see http://www.chrisjohnsonphotographer.com/charts.shtml and the Ilford Perceptol data sheet). So your negatives would only be one stop over-exposed, less dense and with finer grain to boot. The images shot at ISO 400 might suffer, though.
(Note that a speed-reducing developer is not the same as pulling the film. Using a speed-reducing developer will get you the lower speed but at normal contrast. Pulling will reduce contrast.)
Just be thankful you didn't under-expose by 2 stops...
Last edited by andrew.roos; 01-21-2013 at 10:20 AM. Click to view previous post history.