Too early for me to tell with that much framing done at the shower area.
Get familiar with curves or make a template of the curve(s). Get a bevel guage and you are off to the races. When you mark the wood or other material for cutting, cut outside the line first and then try it for size and appearance. Better lookinn at it than lookinn for it. If it then fits the curves, angles, etc, go ahead and make a final precise cut.
Just take your time and think your way through it before and sort of plan ahead. It's wise to extend lengths at times to accommodate the next area in close proximity to build.
Build it strong in any case to overcome inertia in hard braking or other circumstances. Don't allow any swaying of anything high or low for that matter and you should come up with something that will outlive you.