The 5.1 grains is the max shown in the Alliant Manual, as well.
http://recipes.alliantpowder.com/rg....20%28target%29
That is, however, for a lead semi-wadcutter target load, so it is going to be light.
The load for the 200 grain jacketed hollow point goes from 5.0 to 7.1 grains of Unique, so you can start GRADUALLY stepping the load up.
Lead loads generally generate less pressure than jacketed loads due to the hardness of the copper jacket vs. soft lead, but you still have to be careful in what you're doing.