If you have modern GS skis and you know how to carve them through the turn, reaching FIS limits on the lifter and boot sole thickness will be beneficial.
If you are just getting into the racing at Masters level, I doubt you will notice the difference between 47 and 50 mm, especially if you are used to skiing without lifters.
BTW what is the ski and what are the lifters you are considering? Most GS skis nowadays come with the lifter plates and after you put recommended bindings on them, you are at FIS limit. The boot sole thickness is the one that usually requires more attention. Some "Carving" boots have the boot sole thickness that exceeds FIS limit. Racing boots however are built so that they are 3-5 mm under the FIS limit with the production liner allowing for custom footbeds. After your boot is fitted you can measure the actual thickness of your bootsole. Some boot manufacturers (Lange, Atomic) supply plates in different thicknesses, that can be screwed to the sole of your boot and put you right at FIS limit. Those can be obtained through the race department, and have to be installed by knowledgeable tech, since it requires some grinding.
Hope that helps