I think you are in the ball park with 7-11 for most longbows but recurves tend to be much higher this is also for takedown bows, not sure how I would measure this with a one piece bow.
Changed my takedown bows a few years ago by 3 degrees. Performance difference was incredible and the same limb thickness was about 10 # heavier with less slope. Not too hard to make a few test risers out of cheep maple and do a few force draw curves with the same set of limbs.
The only problem is once ya got that figured out then you start changing taper rates, length,adding power lams... and you get to thinking again " now what is the best riser angle for these limbs?" and it all starts over again...
Good luck and keep us posted with what ya do