You can't make it thicker than that. I don't put them on the box, instead I fix them to the top first. The brace that goes under the fingerboard, which crosses at its end, is straight and flat. The other one I give a little arch to give the top a little dome upwards. The reason for this is for when the strings are tuned, the string tension won't try to bend the top between the bridge and the soundhole.
Some builders make it straight.
Then, what happens, when they tune the cuatro the top eventually sinks into a downward bow, That's when the bridges twist and problems start. I've then got to adapt the bridge to that bow. I can't put on a flat bridge, I got to match it to the hollow of the top. The fingerboard For the fingerboard, if I have ebony, I can use ebony. If I don't have ebony, I use native woods such as maga.