The optimum percents are 53% left and rear and then adjust your cross for driver preference. Wheel weights for those numbers are as follows.
This gives you 50% cross.
You can get the numbers from the reverse scale in the tool box here on this site.
If you dont have a set of scales there is a diagram to build a set that will use bathroom scales. I have built a set. I also wrote an excel spreadsheet for use with them.