Were going to be drilling hols through the roof a Toyota echo (echo echo echo) sticking bolts through and slapping some wood on there.
My friends parents used to put wooden roof racks on all there cars to move there canoes around they would nail old carpet to them to for a better contact surface on the boats.
As for the "structural integrity" of these racks you get what you pay for, I spent about 14 Canadian dollars.
Step 1: What You Are Going to Want
Wood this will be different depending on your cars size and what you want, I used a pallet because its cheep and already cut to the right size for me.
2 four ft long 2x4s
8 little spacer blocks
A Drill with a metal bit I used a 1/2 inch bit
Ratchet set and Wrench (or two wrenches)
4 long bolts, I used 6 inch long 1/2 inch bolts and two 5 inch bolts because that's what I had, you will probably want to user 4 of the same size.
8 large washers, mine are about 3 inches wide
A tube of caulking or some kind of water proof sealant
Measuring tape and marker (if your into that kind of thing)
Something flat to get the roof carpet off
Step 2: Move Your Roof Carpet Out of the Way
My roof carpet is held in with these little tool less plastic clips, then just tucked into the plastic around the windows, so I was able to pop the clips out and roll the carpet forward. If your not lucky enough to drive an echo (echo echo echo) this might be a lot harder and you might decide that you just don't care and want to cut. My friends parents would never put the carpet back in.
Step 3: Drill Your Holes
Measure where you wand your holes (or like whatever) then drill baby drill!
Step 4: Drill Your Wood
Were going to want to line up the holes in your wood with the holes in your car I recommend a measuring tape for this (or like whatever)
Step 5: Seal Your Hole Unless You Think Rain Is a Conspiracy Theory
Calk the inside and the outside of your hole
Slip a washer on the inside then slide a bolt through
Step 6: Slid Your Pre Drilled Wood Onto the Bolts
With a wrench on the bolt inside inside your car use a ratchet or wrench to tighten the nuts on the outside.
Step 7: Put Your Roof Carpet Back On
Now spray paint your hubcaps gold and wait for all the accolades and notes from your small town
neighbors to roll in.