I think the question need to be asked: the term "kit" usually refers to a collection, a bag of parts. Are you planning to "kit" this up for resell? a gift? a sample? For someone else to build?
Or, are you 'kitting' it up for yourself to build; essentially doing a 'scratch build'? If so, cutting & slotting the tubes yourself should be half the fun! A lot of us do it, and a few kits did have you slot tubes for fins. I believe it's a skill that's expected at some point in the hobby!
Then speak to your expected tube supplier. They can (and should) add this in as a 'value added service' for the tubes you buy. You may want to seek out the supplier's supplier.. For the qtys you're after, and the customizations as well..