1/16" of side plate thickness can equal 4-5# of spine.Regardless,it can still be tuned with point weight.
I just took my 48# recurve out that is similar in cut.My 2018's have brass inserts installed so the lowest I can go is about 195 total weight on the front and they are showing weak.
Are you shooting bare shafts?What reaction are you getting that tells you they are weak.
OL Adcock always said if you keep changing point weight and the problem doesn't go away,you went the wrong direction.
I would try lighter points to either rule that in or out,before going further.If that makes it worse,then you know they are definitely too stiff but 300 grs wasn't enough.