Sorry, why not remove the pan and lay the flooring under it?
If you insist on cutting around it you will have a long cut at the back of the pan to the wall. That is silly.
Do you plan to remove the existing laminate flooring first?
I respect the fact that you go to the trouble of posting here first, kudos, but I don't think that you are always totally open about what you are doing. IMO laying a vinyl sheet over existing laminate flooring is a bad idea.
I get that you are trying to earn a living but do you really think it fair that some (but not all) of your customers are "experiments"? I do not doubt that as time passes, you will earn your spurs, but... seriously mate, do you want to be the guy that chuffed up a number of houses in the process ?