The PDF for the Orion filter set is a good visual reference when mixing the Wratten filters. It shows representative spectra for the various filters as graphs. It appears as though the combination would give a #56 light green type with less blue and higher transmission.
A more complete table version can be found here. You can just multiply the respective transmissions (as percentages) at each wavelength to get the combined transmission.
Honestly though, just stacking them and seeing whether they work nicely is usually easier. You can even do that after the eyepiece for a quick check before you take off the eyepiece and screw one, the other, or both on. The charts and graphs are better for finding totally incompatible pairs where the spectrum of one kills a large part of the other.