A 28 inch tibia is almost twice as long as normal. A skull 15 inches from chin to crown is also about double. If these dimensions are accurate that would be a very large person. Lots of reports do exist with these limb dimensions considerably exceeding 20 inches, and these are the reports I find potentially interesting if any primary sources could be tracked, as it tends to suggest an actual very large individual rather than the occasional instances of normal sized bones being miscalculated, or a skeleton stretching in situ in the grave and disarticulating. More data is needed to resolve these questions.