A mounting device (100) for installation on a hollow rib of a panel is disclosed. The mounting device (100) includes a mounting body (102), an insert (160), and at least one clamping fastener (180). The mounting body (102) includes an upper section or base (104), along with a first leg (112) and a second leg (122) that each extend downwardly from the base (104) in at least generally diverging relation to one another. The first leg (112) includes a first projection (116) positionable in a recess on one sidewall of a rib, while the insert (160) includes a second projection (164) positionable in a recess on the opposite sidewall of this same rib. The clamping fastener(s) (180) extends through the second leg (122) of the mounting body (102) and forces the insert (160) in the direction of the first leg (112) of the mounting body (102).