Just getting started on the rack for my 2003 liberty.
I'm using 1" square bars attached to the bed rails from a queen-sized bed frame - pretty strong stuff actually. I chopped the headboard supports to be flush with the bottom of the rack but retained some to make attachment of lights super easy. I will be thinking up a way to move both front floods to one side for camp light, but for now they are pointed to the front and slightly out (they are Amazon specials). There is a 22" light bar on at the rear also.
So far, I have only attached the front and rear bars to the longitudinals, but am planning to add 4 more cross bars. edit: might be doing coarse wire mesh if I can find something thick enough.
Currently it is 79" in length, around 38" wide rear, 40" front. It hugs the roof pretty closely and is attached to the stock rails at the rear with 2" width u-bolts and at the front with 2.5" width u-bolts. In addition to more cross bars, I will also add 8" vertical supports to the sides and bars running the length of the rack, with the bar angling down to the front lights/front of the rack in the front 22 or so inches. I will not add any taller parts front and rear so as to make canoe mounting lower and to reduce wind noise.
Welded it up with an old Canadian Tire fluxcore 110V.