mounting wood storm windows

[redline9k]

Working on building wood storm windows to improve the drafty original 1890s windows until I have time to rebuilt/re-weatherstrip those.

Just doing a basic frame of Doug fir with M&T joints, glued (no pins). Everything is going well on my "test" window - the frame is bowed pretty noticably in the middle, but its 125+ yrs old so i guess thats what you get. The real question is how to mount these. The jamb is pretty recessed from the face, so regular storm hangers wont work. Maybe just a pair of eyes top and bottom with a small shim in each bottom corner to hold the frame tight against the top and allow a small air gap for condensation?

any better ideas?