Just to add a little more on the boom height and aft head location:
Boom height – possibly fit a sliding gooseneck so you can raise the boom height when deploying Bimini – see my post A169 last year as part of the mast rebuild.
Aft cabin toilet:
I know of 3 aft cabin loos including my current arrangement – installation of this is described with photos in a previous post for A169 and in a bulletin; also had this arrangement on A100 – you can read the Sailing Today magazine article, (under A100) which has photos and commentary on the setup. Personally, I find the location far better than the fore peak arrangement.