Not that I have much experience tinkering with bike suspensions but, a forward rake does lighten the rear end. Pickup trucks are usually raked forward to take some load off the rear springs so they can accommodate heavy cargo. Under what circumstances are you losing traction? Mild/heavy cornering, braking, etc?
I'd recommend resetting them to factory spec and then tuning it to your weight and ride preference.
Btw, just to rule out the obvious, how's your rear tire look?
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