I'll have to add my 2cents to this one.
Powderburner makes a couple good points..
....don't be afraid to throw it away and start over it's only paper!
....multi layer nesting shroulds is a great way to add some strength and a load of weight to the model.. but IS NO at all necessary.
There are a number of models that are/were entirely made of cardstock in the 65lb to 115lb class that have NO additional reinforcment at all... NO CA soak, NO fiberglass, Not even an overcoat of glue.
Centuri experimented and released several all cardstock kits, Quest has put out a few and many of us have been using the technique for years in Nar competition as well as sport flying. Sometimes on a very long Scale model transitions, where fins or other things are also being attached addition strength may be needed but for a straight shoulder or tailcone transition they should be fine just like they are. Models like "the Point, Vulcan, X-24 Bug, DCX, and several others are made entirely of 65lb cardstock, some with a central bodytube some without any other structure.. they fly and last just fine. Look at Fliskits "Midnight Express" it's all paper construction works just fine.
Don't let the overbuilders scare you into thinking a Paper, cardstock or light ply shroud, transition or nose cone are to fragile to fly... they are not, and work wonderfully for many flights. Many competition flyers use tracing vellum "paper tigers" in parachute, streamer and eggloft events to level the playing field with the single wrap fibreglass lay-up's the BTC's use. I know I'm one of them, and they can WIN
What do you think powder? a D12 Pd model made of single wrap of 100% Rag tracing vellum with the seam held with plain old Magic transparent tape? it works, is reuseable and very very light
or a better example a dual egglofter with a 13" body taper shroud made of poster paper, again magic tape attached to a 24mm 3" long piece of body tube/ motor mount. This same model has flown in at least 5 meets over the past 6 ro 7 years.
Here's a composite pic of several different all paper or cardstock models, including a cluster altitude model with tracing paper transition.
Hope this helps