This is the correct way to mount them.......travel is forward to back , not up and down.
The car is on stands in the pic , which is why they are all the way forward.
They settle to about 1/2 way in the travel when it is on the ground.
To mount them outside the frame rail would require some fabbing.........making a small " platform " for them to sit on and attaching it to the frame.
But it wouldn't be too difficult I think.