24 and a stabilizer arm 74 extends through a slot 78 in the upper end of the diverter 72 the diverter 72 is secured to the base plate 24 by the stabilizer arm 74 a brace member 44 and stop members 79 as described below with particular attention to fig9 and 10 a slot 73 in the lower end of the diverter 72 mounts over the web 36 of the base plate 24 the slot 73 is positioned between a forward brace member 44 and a stop member 79 both of which are secured to the web 36 the lower end of the diverter member 42 thus has some freedom of movement between the rigidly secured brace member 44 and the stop member 79 wing pieces 46 may be mounted to the diverter webs 42 as desired a forward end of the stabilizer arm 74 mounts to the upright web 36 of the base plate 24 aft of the serrations 38 a mid portion of the stabilizer arm 74 is fitted into a slot 78 at the upper end of the diverter 72 between an aperture 29 and a stop member 79 that projects from the stabilizer arm 74 the stabilizer arm 74 is secured to the upright brace member 44 at the aperture 29 the brace member 44 is vertically aligned to the intersecting edge of the web pieces 76 of the diverter 72 an aft end of the stabilizer arm 74 extends through and floats in the upper slot 78 in the diverter.