Finished my first shoe today and i agree with other folks saying these just aren't there yet for comfort. Here are my suggestions. - Remove the back completely. Thats what the straps are for. - Most people are going to print these in a harder TPU. which makes them too rigid, so try and create more flex points where they aren't so thick. Specifically the top and the arch. - The bottom needs work too. The current voids/grip don't print great, so a more wavy effect might be better as well as removing the totaly flat part on the arch. Go way thinner there. - My preference would be also have a printed insert of a really soft TPU, but that could be optional. Overall its really cool and i'm excited to see more shoes. I would be happy to help make some changes if you wanted to work on it together.