Rule 19, Quality Control, allows the team to ask the referee to check the setup and confirm that mission models are in the proper place and locked down (when appropriate).
-- During your pre-match setup time only, you may ask the ref to double-check that a particular setup is correct/within spec, but you may not request any custom setup, in or out of the specified setup range.
All teams are encouraged to inspect the field when they arrive at the table, and to point out anything that looks funny to the referee.
I don't recommend that teams ask the referees to check every model each time they come to the table. That presumes that the referees aren't doing their job maintaining the table, and it gets tedious, and it uses up all the team's setup time (or more!) But definitely ask the referee to double-check the models that you know your robot has trouble with. (And the first team of the day in the Practice round might want to be extra vigilant!)
If the water bottle is close to the end of the truck, it's okay to say, "I know that we cannot request a custom setup, but we are concerned that the water bottle might roll out of the truck. Would you check that all items are safely within the truck, and that the sides are on tightly?" Most referees will pick up the truck to look at it and set it down again, likely with items safely contained in the bed of the truck. (The Variability rule, Rule 42, may still come into play with any match setup, of course.)
Steve Scherr
VA/DC FLL Referee Advisor