I've only done salmon with phyllo. With Beef it calls for puff pastry....similar but different. I think puff pastry is a lot more forgiving with respect to juices. I really don't think that juices were an issue for me. As I said I should have used a smaller piece of beef or rolled the puff pastry out a little bigger. Beef Wellington is wrapped in paper thin ham and a crumble which is made up of mushrooms and garlic ran through a food processor and cooked to remove any moisture. I think this picks up a lot of the juice.