I just went through this with a an E-Yak 54 from QuiQue Somenzini's website. These things are designed to be very lightweight. Unfortunately they can twist when they are covered and with changes in humidity. Try gently clamping one end of the fuse to your workbench (I just used a book to hold it down) with the rest of the fuse hanging off. Gently twist the fuselage to slightly past staraight and use your heat gun to re-shrink the covering. Keep holding it until the covering cools. It may take a few trys and it's frustrating but it can be done. Perhaps some others will have additional ideas.