I see your concern is board strength across width. So focus reinforcing it cross grain. If you go for 2 sheets like RalfsB suggested, try using a uni-directional piece cross grain and normal weave over it. FG cloths are ussually 1m wide, so this can be the length of your UD patch. But don't go for strict center, because the foot position is offset toward the tail.
p.s.: I also use hardener, which is slightly bluish-greenish (very similar as UV blocker additives) but the mix is perfectly clear. Cheap epoxy yellow does not look good. Anyhow in reality UV will discolor and/or enhance some colors, so it wont look entirely the same after a while.
Nice looking board BTW! I like your tail cut