You don't need to harden the mix to increase your bullet size in existing molds. Just "Beagle" it using aluminum tape. If you do a search for the technique you will find ample info. I use it on one of my Sharps molds, an RCBS, which (typical) casts undersize.
You can bias the stop point of your bullet in the Star so that it only encounters the one point but be sure your dies have only one row of lube holes open. If you do you might move it down to a lower single hole point so that you are fully into the sizing point of the die. Also; running the lube too hot can do that too.