Yesterday I just finished a four day tour with an almost identical setup. The handling felt very wobbly when going at speed which made descents a bit on the uncomfortable side. When standing, the bike shifted side to side significantly more than when unloaded but you can easily learn to compensate this.
Like you I also heard about the 60/40 rule of weight distribution and expected the handling to be wobbly and wasn't let down. I just got my front rack in the mail yesterday (good timing, I know) so today I'm going to load the bike up and head for some hills and see what the difference is.