I have a general question on the realistic constraints of using Hibernate for complex multi table queries versus using Hibernates own search mechanisms.

My Spring web app uses Hibernate to map all the entities and for simple CRUD operations or one/two/three table queries and master/detail associations this works fine. However, I've now started to add some quite complicated reporting facilities to my app that often join 6 to 10 tables. Doing all of this in Hibernate HQL is starting to get cumbersome, and I've even had the Hibernate tier crash a couple of times trying to process these large queries. Building the same queries in plain SQL is easier and seems to work faster.

I'm seeking some general advice on how best to approach this problem. Are there recognized constraints about where to best employ and not employ Hibernate?