I always think mid-knee is the best length on most people, but some guys look quite nice in a shorter length, and it's really all up to you and what you like. I agree with some of the previous comments that if you wear the waist at navel height, as it's supposed to be, you may find the length is all right. The general rule of thumb used by kiltmakers to determine if they've been given an accurate measurement by an absent customer is that the length is about 1/3 of the person's height, which for you would be 24.5 inches. That's a fairly long kilt. I think 24" is probably a better length for you, if you have average proportions in your build.

Having a kilt shortened is not such an easy thing, because it has to be taken off the waistband -- a traditional kilt should not be hemmed; it won't hang right or look right; it needs to have a selvedge at the bottom. But it can be shortened at the waist by a kiltmaker, certainly.

To measure for the length of a new kilt, kneel on the floor with upright posture and have someone else measure from your navel to the floor with a yardstick or metrestick. Then subtract one inch from the measurement to give you a mid-knee length -- adjust accordingly if you prefer the kilt shorter or longer.