I like soloing in the rear seat but it doesn't like me!
It's just my weight. I can run things just fine from the back if someone else is on with me but solo the bow rises up so high the wind pushes me all over the place and the rudder can't compensate below 3.5-4 MPH. I did manage a reasonable run from the back seat and also found the hull slapped the face of every wave - very annoying!
Adding some ballast up front should do the trick too, of course, but I haven't tried it yet.
What did you modify on the furler? I've always just tied the end of the furling line to the end of the main sheet at whichever position I used and it works just fine. Have to give the line a fairly good upward "pop" at times to get it to uncleat but otherwise no trouble for me.
I kind of wish I'd settle on one seat - front or back - because I'm really tempted to do the 3:1 conversion on the main. Sometimes it gets mighty tough pulling on that rope!