Moving the CG aft (take out nose weight) will make the response much better. I am not familiar with your ship as you might need a incidence adjustment. Also when you do that take out ever so slightly the weight until it gets unstable. It sounds like the CG is OK but if controls are usually sluggish it's usually nose heavy.

Another consideration is fighting the slope is the the air is rough to start with and a seasoned pro makes it look smooth as he is constantly on the controls but ever so slightly. Over control is ones worst enemy and in time you will get over that.

Keep in mind you say thats a slope racer and the controls will be slow until you reach up-wards to 80mph+. At those speeds that thing will roll in no time and the elevator will be quite responsive. At 15mph you should be able to put almost a full load of ballast in that thing and it will really smoke. Get used to the swooshing noise as thats a sign the wing is doing its job. At high speeds the air is not happy. At even higher speeds 120+ you start to get the shrieking noise which is a Erie sound and takes some getting used to.

Keep the weight out of it for now and get some stick time in. Play with the CG (Trim it out)a little more and if the wind was 5 to 10 it would be less likely to get bounced around. Just remember when you add the ballast it will land much faster but I am most certain it will fly very stable.

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EC