That brace is kinda useless and double stacking the baffle would be better.
Plus if you are going to compete in spl comps, 60hz tuning frequency would make a mucchchhhhhhh higher number on a termlab. I would take a guess that you would be ~155db @65hz as opposed to ~145db at 42hz.
And a tuning freq of 28hz with your enclosure in the right orientation would give you a range of 25hz-80hz as opposed to falling off from 40hz down and only playing with authority down to 35hz.
I am just trying to help, Build a SPL box and a box for Daily use and music. Swap for comps.