Hi H.,
Couple of suggestions, if your dealing with a lot of clay, I would get the regular 48" Propector with the longer slick plate. Then I would attach a piece of hardware cloth or small expanded metal at the top end. This is to aid in breaking up the clay, you can literally slam it down onto the sluice. If I had to come up with one disadvantage to a fluid bed style sluice, it would be you don't have anything breaking up the clay. Second suggestion, don't worry a out needing a heavier construction, these suckers are tough. You know where I was using mine (actually I've moved way up now towards I----p) but it takes a severe beating, it's taken more then one solo trip down to the river from up by the flumes.
Best of luck whatever you decide, your gonna love it.
PS- When you gonna head this way?