This one is a bandaged 5x5x5, into a cubic 3x3x5 yes? You must have capped/ filled the little fillets in between the bandaged pieces yes? How did you do that without adding any visible thickness?
I had to do a similar thing when I did my 3x3x5 from a 3x3x4. In the joint between the pieces, I opened it up slightly with a 3-square file, and then filled the groove with Apoxie Sculpt. After sanding, moothing and polishing, the joins were almost invisible.