The geometry does look similar to mine, but could different enough for you needing a heavier spring. I have the option to install 3 different shock lengths on my frame. The bike manufacturer has a list of spring rates depending on the shock position, shock length and rider's weight. In my case it's around 400lbs with the 9.5"x3" shock for offroad use. I had a heavier spring before and wasn't good with the bike seat vs when I had the moto seat installed. I use lighter springs for onroad use. The Titanium spring behaves the fastest on higher speed runs.
That 750lbs sounds a bit much for you.
That 750lbs sounds a bit much for you.