I have a similar problem (left femur shorter by ~.75 inches or 20mm). It isn't easy to correct for this problem, compared to having the difference in the lower leg. The trick is to try to compensate to some degree during the power phase of the stroke, without making it worse elsewhere. There is no way to make the entire stroke match your other leg, but you can get close. This is what I tried:

5mm shorter crank on the left.
5mm shim on the left.
5mm forward cleat adjustment on the left.

At 0 degrees (top) I have zero vertical correction because the crank length and spacer cancel out (good!) and 5mm of horizontal correction from the cleat adjustment, which directly helps compensate for my short femur.
At 90 degrees (power stroke) I have 5mm of vertical correction from the cleat shim and 10mm of horizontal correction. Both of these help compensate for my short femur.
At 180 degrees I have 10mm of vertical correction from the shim and short crank, plus 5mm of horizontal correction from the shim position. Since my leg is almost fully extended at this point, the correction is pretty good.
At 270 degrees I have zero horizontal correction, and 5mm of vertical correction... this is not ideal, but it's the best I can do.

Note that I'm only correcting for about half of the actual leg difference... and for you it would be even less than half... but I think this is a good place to start.