10INT = 200MP which is equivalent to 100HP mana shield
10STR = 35HP
100/35 = 2.8571
When you get to the point that you can add every 3STR in exchange of every 1INT, then adding STR is still good.
When you get to the point that you can only add every 2STR in exchange of every 1INT, then adding STR is bad.
So you can shift one of your highest stat to some STR (no more than 50), but in many case where I learned the accuracy passive, which is based on INT as well, if INT was the highest stat for the stat build, then need to think twice before shifting them to STR.
I don't know if the Rescudo stat calculator is still up at this forum for download, but I think I don't have permission to re-distribute it.