IMHO, If I were you, I would consider going to Blackhorh 209s wed site and read up on this great powder, many of your questions will be answered from the source of the powder.
You already have internet access to post here, so a simple search of "Blackhorn 209" will easily find their web site full of the manufactures recommendations and FAQ , and load data, does and don'ts.
I personally find a load of 80 gr V to be more than adequate for all of my BH209 needs. I find no need to magnumize, and as already posted it is easier on the bank account.