Howdy,
I am setting up my first longbow and have some questions. It seems the bow is a lot more sensitive to shooting form and arrow selection than I was expecting. Early on I think a lot of the inconsistencies were my shooting but I got a handle on that. Now I'm seeing subtle differences in the arrow. Any ideas on how much decrease in spine I get by going from 160 to 190 gr points? How does a 45-50lb spine arra with a 190 gr point compare to a 40-45lb spine arrow with a 160 gr point, all else being equal? Can I compensate for a slighly weak or slightly stiff arra with brace height? Thanks in advance.

160 to 190 makes about 3-5 lbs spine difference for me and my longbows in the 50 lb range.  You will definitely lower your dynamic spine going up 30 gr in point weight, how much seems to depend on shooter, bow, draw weight and arrow length.  It would take MANY hours of paper tuning with several shooters and combos to come up with really close values for different specs.

The Stu Miller arrow computer says you can use brace to tune arrows.  I like my brace where the bow shoots best and quietest.  I work with spine, arrow length and point weight to get my arrows flying right.  Paper tuning is my method of choice.

I had a bow that was super sensitive to arrow spine and shooting form, I tried to match arrows to it for months. In the end I glued a thin piece of leather over the existing strike plate and all the problems went away, it is one of my best shooters now