Im now Im making worms like world destruction.
My solution is based on ashley's destructible terrain trick.
So previously fired projectile gets removed when it hits canvas and spawns erase sprite. That sprite is pasted on canvas and then canvas updates its collision mask. Everything works with 4-5 first explosions but when canvas prop gets destroyed to about 1/2 its thickness projectiles collides with previously erased parts of canvas , and then crash commits. Im using latest construct version.