I did this with Technic stuff, tho not leather.
The legs were too long and dragged in the dirt over boots.
The trouble is that any armor/reinforcements on the knees will be moved when shortened above the knee.
In hindsight, the armour cups on the knees were correct on the bike but descended off of it, (leg length seems to be longer bent which hikes up the pants). I had 1.5" cut out of a seam above the knees which solved the length problem. They are correct when I stand upright, but hiked the knee joint/armor above my knees when on the bike.
Now they are too tight in the knees for long distance.
I'm not sure what the solution to this is.
A cut in panel would alleviate the tightness, but destroy waterproofing. It would also allow the reinforced part to be pushed/rotated away on crash contact and thus useless even whith straight legs.
Anybody else have ideas on this.
It seems most of this stuff is designed for Six foot guys who weight 150 lbs.
I may post this thread by itself if others deem it worthwhile.
Mike, waiting for spring but still sking!