Anthouse.es 'Modular 3D Kit' Stopper/Conector

I got the Modular 3D Kit from anthouse.es but although I really like the design, i don't like the stoppers/tunnel connections, they don't feel very secure and easy to fall off.

So i designed these for a better fit.

Unfortunately anthouse.es no longer sells this model on the site, so no future expansion will be possible