Is the quilting in the borders not the same as what we can see on the Pirates shirt?
One option would be to dampen it down and use T-pins to block it out on carpet, or on a drop cloth on the lawn, that is what many people do for show quilts.
Another original problem might have been border and backing that weren't prewashed and shrank?
It does appear that corner is shorter, but as above, unless it is a wall quilt no one will ever notice or care.