I bought an Iron Gym just for this purpose. Every movement in the book is possible.
The official site is: www.getirongym.com but I got mine at Bed Bath and Beyond.
The infomercial presentation made me hesitant, but it works.
Hang the ring straps from the part of the curved bar that extends out. This allows clearance from the door frame for a full range of movement.
which has more clearance from door for assist cross pulls. Do you find it secure? (obviously not for kipping pull ups, but i mean controlled work)