Will this shoe fit without fastening

So I am working on my favorite shoe that finally wore out. And made a sneaker look out of leather. But the original shoe is like a croc material that is similar to croslite which is spongy injected foam. That’s nice and soft and keeps it’s shape. After all this work I did not think about the opening – duh! ! Because i followed the original! Now I am not sure if my foot will fit. It did on my sample but that was with no lining and stuff and it stretched.

My question is – if this turns out to be a big major mistake how would you correct the opening? Or back to the drawing board.  I used some of your techniques
ps yes I am putting a shank in the shoe I did follow some rules “SOLUTION “