The older estes plans have a VERY good parts list inventory. Each part is has a designation (eg. BT50-H BNC50-Y etc.). The newer plans just say "body tube" "nose cone" and rather useless info. With a download of this gem:
https://plans.rocketshoppe.com/pubs/Estes/Estes_Custom_Model_Rocket_Parts_Catalog.pdf
You will be able to see each and every spec of each and every Estes part... Not only that, e-rockets (eg. Semroc) has kept those designations and in many cases the parts are already the appropriate size. With the custom parts catalog, you can spec out and cut your own tubes to the proper lengh... BMS and Semroc have virtually all the nose cones transitions etc.. I *just* purchased the transition and nose cone and pre- cut tubes for the ancient Estes Thor-Agena B (those items in the very old kit I bought aeons ago were damaged by mice in my garage!) The Thor
wil get built!!!
I also got all the parts I needed to build a perfect clone of the Estes K21 Gemini Titan including the centering rings.