I would leave the taller gearing. I tried 19:51 and it was way too low for my liking.
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What clicker are you running? What rpm? What ramp and primary spring? A stiffer primary spring would likely be more prone to slippage unless you are not close to getting proper peak rpm now.
Make sure to scotchbrite the sheaves and the belt if they have seen a lot of heat...they get a glaze that will cause them to slip.
The gearing should be OK.
The helix is the one unknown....it might not hurt to get a 43/47 just to eliminate that as a possible cause. Are you running the complete setup that trask recommends....primary and secondary?