If it's your dad's why don't you ask him to measure it. You should keep the front and rear the same. If the front is higher you could also get real bad head shake causing you to wreck. If you can't get some thing to make sure they are both the same then I would just leave it stock or take it some where that can do it for you. Like you said just to be safe.me too man. But here is the thing to match the front to the rear, I have to drop the front by a lot. I'm talking 2". Well when you do that You don't have anything to go by as far as to see if the left and the right fork are even. My dad have the special tool to measure thing down to the micro meeter. I don't think he'll let me use that to test out my bike. He use it for for and it's a lot of money.
If I go by a ruler, which I did the last time. My left and right turn don't seem to balance each other. That's why I've raise it back to the 3rd line on the fork that is indicated by Yamaha.
I've ask other rider to see if it's ok for the front to be higher than the rear. He said that it's dangerous because you're more prone to having a wheelie if you're not careful. Which I don't need.
I'll take any input people. Just want to be safe.