In order to determine if I can shorten your cranks I need a few measurements, and some photos.

If there is a recess on the back of the arms, I'll need to know the depth of the recess at a point 23mm below the pedal eye. A photo would also be useful.

Any model numbers on the back of the crankarms will help me identify them.
For instance Shimano Ultegra 6400 series can't be shortened, but Shimano Ultegra 6500 series can.

A couple of other photos, looking down the arms, front and back, will show me what the cross sectional shape is like at the new location.
Put a piece of contrasting tape. on the arm (also at about 3/4") to make the shape more visible.

In this example, the width and thickness would have been adequate with a more rectangular shape. But the large bevels reduced the amount of metal available in the corners, just where it would be most effective in resisting bending loads.

WRONG,
A straight on shot like this doesn't tell me much about the contours.

With it I can use PhotoShop to copy the pedal eye to the potential new location.

The ruler was a nice touch, but as you can see, this one goes into the NO column.