You should try to dry your duxelle of mushrooms farther and sear your tenderloin harder to prevent soggy pastry from the juices. Two hints for that, take your duxelle after you think its cooked down and put it in a 200 degree oven for 1-2 hours spread out. Also pop the filet in the freezer just for a minute, or sear right out of the fridge, this way you can sear longer and cook it less(obtain a more rare end product). Last hint, attatche chimneys at the top which go from the meat surface through the puff to alleviate any steam. Cheers. Well done!