Add up your height in inches. There is 12" to a foot. We'll use my hieght for the example. I am 5'11" which equals 71 inches.
Divide that by 86: 71/86 = .82558
Multiply that number times the scale it currently is, 30.342: 30.342*0.82558 = 25.04979
Now in Pepakura, go into 2dPatternWindow and select "Scale Up/Down by specifying value"
Under scale, put in the new scale (for this equazion its 25.04979). Do this for all of your pieces to be symmetrical.
One thing to keep in mind
The size of the scale that is in use before you edit it is from the base of the ground to the top outside of MC's helmet. You don't really want the top of your head to be touching the top of the inside of the helmet if you expect it to fit right. So you may want to add two or three inches to your actual hieght before doing the math. This may help other areas as well, where it could come through a bit tight.