Interior Patterns - Required?

I have heard that you should make patterns of your interior from cardboard prior to adding systems, i.e. fit the cardoard between stiffeners and longerons in the cockpit and cut so they just fit. These can then be used later to size and make interior panels.

My question is whether this is necessary if you're buying a storebought interior? I would think that prepunched kits are all the same, and if they (flightline interiors, etc) have the patterns for one RV-7, they have them for all RV-7s - true??

Abby (Flightline) has the 7 down pat and I am sure the other models as well. The stuff she sold me fit just fine. Now if you do any deviating from the plans, your on your own....