Abstract: An improved panel mounting molding for framing interior storm windows of the type including a base adhesively secured to a window frame and an interlocking pane biasing strip for holding an insulating window pane against the base. Improvements include a biasing strip anchoring arrangement comprising a channel formed on said base in which the inside channel walls each carry three opposed ridges and a corresponding anchor on the biasing strip having three corresponding grooves for mating with the ridges in the anchoring channel. The biasing strip may be anchored to the base in at least two different positions providing a wide range of useful pane thicknesses.