Definitely 4", 1" space on all sides. I would, however, wait until the plant produces a new set of roots. Wait for a new growth and when you see the 1/4" new roots emerge, then transplant it. If you do it now, the plant will probably sit there, inactive, until the next new growth emerges. If there is lots of new root activity right now, then do it now.

I collect species but have 3 daughters and a daughter in law who can't get enough of Catt hybrids. They raid my place regularly hauling them off to decorate their homes. For some reason, a beautiful Stelis or Scaphosepalum does not do it for them. I finally got them trained to water properly and return the plants in good shape.

Mostly for them I bought a bunch of Catt hybrids from Kawamoto the last couple of years. He used to hold the plants and ship once a month. When that box full of healthy, robust, large plants arrived it was like Xmas. Many of them are in first bloom right now, these women are very happy. I'm a big fan of Kawamoto, their customer service is outstanding.

Nick