Unless you found a published load for 20.5 grs., would add 6.5 more grains. Going below MIN. is just as dangerous as going over MAX. Good luck.
I had actually talked to a tech at hodgdon powder who told me that with the youth loadings for a 30-30 with a 150 grain bullet 20.4 grains of H4895 was the start load. So i notched it up a tenth
they have a 60% rule aslong as you use atleast 60% of a maximum charge its considered safe according to hodgdon. I did ask the tech, that 20.4 grains seemed too low but he assured me its safe.