Have you contacted DSS yet? The first one I installed had a minor shake at around 30mph. I called them and they sent me a replacement pretty quick.
'14 F150 4x4 SuperCrew 302
'11 GT MT w/ 3.73s and some bolt-ons 550 RWHP / 490 RWTQ 11.94 @ 123, 1.84 60 ft. Wannabe Sleeper