The Tamiya rack & pinion lift on this trk is somewhat limited in travel & won't completely dump a wet load without jerking it off, but lift power it is not short of! The Firgelli linear servos would certainly remedy tipping the box higher & Firgelli's have built in limit switches making them dummy proof to use. Not sure what stroke or ratio to get for the right balance of lift power & speed.
Your lift still not working the way I described to you?