I actually agree with you that it is a trimac now that i actually take time and look at my pictures, this is because of the mouth and also the consistent coloring in the underside of the fish below the gills. also the spots on the rear protion of the body are consistent with the pictures i found, he is a little skiny i figure thats because the pictures i have are of trimac about 10"-12" .
i also belive trimac, the spots, and the coloration, i know flower horn have those spots too, but i do believe you got a trimac, and a excelent deal at that size