This link suggests with 1:10" you would want 90-100gr bullets
with a 1:8" 105-107grs.
And my understanding is you can stabilize lighter bullets, its going heavier when you run into problems.
So with a 10" the heaviest you would want to shoot is 100grs, with an 8" 107grs, so with a 9.5" I think 100-105grs would be ideal, and 105 may be even too heavy.
Plus nowadays it seems most .243 factory ammo is 90-100grs, I mostly see 95gr premium bullets loaded, so I wouldn't really push for anything much heavier, if those 100grs shoot great, dont change it up, I don't think 105grs would do much more for you.