If your plywood has the exact same measurements of the original Suzumar including stringers and side joiners you wouldn't be experimenting cruise problems, the fabric floor tightness is given by the perfect fit well aligned tube/floor/top keel, not so much as having tubes correctly inflated, anyway won't know if a manometer is not used to check correct working inflated pressure on tubes and keel.
If you want sibbing perfection ,try to get help from sib mate that has exact sib model and takes the effort and willingness to help give exact measuremnts of plywood pannels, stringers and side joiners including pics. Will be much cheaper than to order original alum pannels that can cost as much as $ 500 depending on the model.
Happy Sibbing
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