The slack in the pushrod travel is definitely an issue. You need to fabricate a longer rod, but don't use just any old bolt or all-thread rod except for checking purposes. Most master cylinder pushrods are made of hardened steel so they won't bend during a panic stop. I'd recommend using a Grade 8 bolt like a cylinder head bolt, etc., something that will be tough enough to resist bending when the brakes are applied "vigorously".
Jerry

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