Adding Additional Weight Option To Kit Products

We have various cut to length products which we create as a kit based off the full roll size. We typically sell in per m and have to weigh the smallest length to determine the weight. However, when we sell a full roll (which we also sell as an option) there is additional product packaging which is not taken into consideration. Could there be a feature that allows additional weight to be added to kit products when sold for shipping weight purposes. We don't want to make the smallest unit/length heavier to compensate for the extra product packaging when we sell this mostly in the smaller lengths without.