"i would hate to give an operator access to something that might get him fired."

i tend to agree rick_c
tampering with speed controls for an enduser (operator) can result in bad things
i have a similar problem with a customer and thier pallet jacks
it seems the operators have figured out the "soft" access to the controls and they keep bumping up the speed, therefore causing problems and we have to keep going out and resetting the controls for the customer because the dimwitts operating the trucks dont seem to understand that what they are doing is causing the problems to begin with.

On a personal/professional note:
there is a service key that can be obtained by the service tech that can access the main menus and enable the lockout option for the user access. IF it were me i'd have a serious conversation with the customers management and encourage them strongly to purchase the service key(have thier tech do so if necessary) and lock out them lamers that keep messin with things they dont need to mess with.

There are some technical things that end users just DONT need to know, i dont care how much they THINK they need to know just to speed up thier production. Safety is the key factor here and some of those guys are just ignorant to that fact it seems!