I've got the Seagull Sapcewalker also, and I found it was pretty touchy on the ground until you got the tail up.

What helped for me was to hold slight rudder while takeing off and kind of pulsing in more rudder to get corrections while the tailwheel is down. Once the tailwheel is up, it'll go easy down the runway with minor rudder input. I have to add in some up elevator to get it to break ground and it definitely will not climb out at 40 degrees. Go for a gentle 20 or 30 degree climb out until you get some more airspeed.

On the throttle, you need to get rolling first then transition fairly quickly to full trottle. It takes me about 3 to 4 seconds between start rolling to full throttle.

I definitely thing replacing the stock tailwheel is a good idea. I personally like the Sullivan one as the spring arm decouples the wheel from the rudder.

Duke