50lb 25” prima with a 444g arrow... micro spines will take more weight to tune than a standard sized shaft, just like a 23mm or 27mm arrow they are stiffer. 
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You’d definitely be at or above 227fps if you add 2.5” of draw... I’d definitely go with a 400 spine standard diameter shaft and max point weight should be 150 or less, point/insert combined. Building an arrow at 400+ grains with a ton of weight up front will be a tuning nightmare and would be way too slow... if you shot a 350ish grain arrow you’d be way faster and not really lose much KE.
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