I built a plane last year. A version of my Slider design. I never really got going trimming it and by the time the season ended last year, I had gotten off flying my Ringmaster Deluxe and never really put any time into it to resolve some of the issues it had.
It's a bit overweight, but not horribly so. It tended to squat on the bottoms of corners and in order to get it to fly anyway near well, I had to really speed it up and wasn't at all happy with that. i was pretty disgusted with it as it seemed it would never really fly very well and it went in the storage rack. I pulled it out a couple of weeks ago and started really working with it. I got the engine finally really running well on a particular prop and while the engine sounded great, it was just going too slow (5.5 second laps) to really have it fly very well at the wing area and weight. So I started chopping the line length (started at 67 feet) about 6" at a time. So, I'm down to 63 feet and it's really coming in finally. Flew it twice today and I'm probably 10 flights from a decent pattern. It's just a matter of balancing the speed, weight and available power. Hey, I'm making progress. At least thing may now be at least serviceable.