* I want to be able to get to shower plumbing from the back. No showers against outer walls please. 

Good [[https://www.boardandvellum.com/blog/common-bathroom-floor-plans-rules-of-thumb/|website]] for bathroom considerations. 

See link above for 6'x6' corner shower half bath. I love it for second bathrooms. Ah! but it's hard to put against outer walls, I want to be able to access shower plumbing from the back. 

lesson 8 in link above, good 3/4 bath is 4'x 8'. Can put shower plumbing in either front or back wall.