According to ANSI Standards there are two different categories for Safety Thickness requirements now through ANSI Z87
These lenses can be ground to a 2.0 CT and need to be tested differently than you have ever tested safety lenses before. It's not the same drop ball type of test. In order to be in compliance with this High Impact 2.0 CT you lens must be test with the high velocity test which you can find out more either through ANSI or another source like Colts Laboratory (they have alot of the info on testing requirements)
The Basic Impact requires at least a 3.0 CT just like you have been talking about. With the same test as before to certify them as passing ANSI Safety Standards.
If you are surfacing safety eyewear you should really know all of the requirements and legalities that you face. There are government regulations on this for a reason even though you might think 1.5 is ok. You shouldn't be able to sell them as safety lenses either if they aren't up to these standards, tested and marked with your logo on the lens. The ANSI Z87 regulations is something that might not be a bad idea to purchase just to know more about what is required of you at the surfacing level and testing procedures etc.