I would cut the recessed tabs off the gutter risers and mount flat on the galley flat. They will be plenty strong with fillets. Take mounting dimensions off the end of the flat for later reference.
If you have a router, esp a plunge router, you could cut new recesses for the riser. At that point you might be all the way through the wood since there would be recesses on both sides, and might as well use a jig saw and cut the recess all the way through and strengthen underside with glass and epoxy after risers are in and filled with thickened epoxy. I would rather do either of those than cut out the flat. That would be NO fun.
