We recently installed Lincoln aluminum clad wood windows and exterior doors on a project.  They function okay but the cladding joints look bad.  the gaps on the joints are anywhere from 1/16″ to 1/8″ and a lot of them have “lippage”, meaning the cladding pieces are not flat when they meet.  Lincoln acknowledged the issue and sent a batch of replacement door leafs – some were better but the rest were worse.  then they sent another batch of replacement door leafs (which they said were fully inspected before they left the shop) but those were as bad or worse.  A few door leafs had jagged aluminum edges sticking out where someone could cut open their hand on.  Lincoln is now saying that’s the best they can do and it is up to their standards.  i have never seen cladding joints this bad.  i have a comparable brand installed on my own home (sierra pacific) and all joints are tight and clean.  Also, we’ve installed Lincolns on other projects in the past two years and those joints were much better than the joints on our current project.  
i can’t find any resources that would define what the acceptable standards of workmanship are on wood clad doors and windows.  what is the maximum gap allowed on cladding joints?  my clients want to pursue a product liability suit but we need some literature that states clearly how cladding joints should be.