just to be clear -- if a host crunching a different project is producing relative RAC greater than the average RAC of GRCStarter@home, and if this host joins GRCStarter@home, they're Mag will most likely decrease.
Any RAC added to GRCStarter@home increase the mag of those with a RAC lower than the GRCStarter Average RAC and decrease the mag of those with a RAC higher than the GRCStarter Average RAC.