Are you working with foam? Before you glue any rounded pieces together, heat form them first. This means taking a heat gun and warming the foam pieces up, then with your hands (or some sort of "foam anvil"), maniuplating them to be more rounded. This means when you glue them together (I recommend using contact cement), there's less stress on them being pulled apart.
Another thing I learnt the other day is to actually do curved surfaces inside out. Take a look at this post by R31 Studios for more info:
501 likes, 12 comments - r31studios on August 2, 2022: "3 tips on keeping your seems shut! There are many more things to consider, but here are some top three that I use a lot. Drop your tips the comments below! 1. Let it cure. This is one of the main reasons seems come unstuck! We don’t have...
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