I installed BAL lock-arm struts. Could not find anything between the I-beams to mount to so I mounted the upper bracket to the underside of the bumper. Works very well and provides side-side and also fore-aft & vertical reduction in movement. I mounted a short length of 2x2 steel to the bumper, then the bracket to that. I haven't installed any struts to the stabilizer (electric) jacks at the front as just adding ones at the rear has made a big improvement and don't think adding one to the front will help all that much.
Can you post photos to give an idea what the challenge is?
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