it would be interesting to know what arrow lengths were used to consistently challenge and set the records in the class you are interested in. I don't know if the record book has the arrow specs, but certainly someone has an educated guess.
shorter arrows are stiffer for their diameter, and aerodynamic theory puts a lot of weight on the diameter factor in addition to less resistance overall for being shorter.
in addition to aerodynamic factors down range, the stiffness/spine is needed for minimizing fletching and having adequate early stabilization out of the bow.
at least, that is how I understand some of the factors.
which of the numerous requirements to make a winning shot is the one that needs the most attention in your set up might be difficult to determine without lots of testing.