I have B/i insulation in my attic. I just put in R-30 batt over the top of it. Where the attic stairs hole is there is a plywood floor over the 2 by 6" joist for storage. I need to remove it to put the rest of the batt insulation down. This area is over the BDRMS. Once I do that, What is te best way to raise the floor / ceiling joist (just part of it) to put the plywood back down to storage boxes itn the sttic without causing a weight problem with the additional lumber or decreasing the insulation value.

Thanks

You can either
Drill 1 1/2" deep holes about every 2' into the edge of a 2x4 then screw the 2x4 to the 2x6 through the holes with 3" deck screws.

Or attach 3"x6"x1/2" plywood gussets to to the side of the 2x6 and the 2x4 about every 3 or 4'. Use construction adhesive between 2x6 and 2x4.

I prefer drilling screwing through the holes but it is more work.