From your description it sounds like you’re trying to copy a rocker. The first question I would ask is “why?”. Regardless, if I wanted to copy a rocker on CAD I’d draw a horizontal line on your background pic for your baseline and maybe put in verticals at either end to set your nose and tail references. It would look like this on your pic: |______|
Then set your nose and tail points on your view and adjust the rocker down or up to “level” the baseline, resetting the nose or rocker reference with each adjustment. You’re basically going to bring the baseline in your pic level with the baseline for your CAD rendering. It would be even easier if you knew what the endpoint measurements were supposed to be and you adjusted your rocker to those numbers to start - then you could just adjust to the curve on your background pic.
No Akushaper expert out here??