Motorcycle Repair: extending the 39mm front end of a 1998 883 and 2001 1200 sportster, metric allen wrench, fork brace

Question
My son and I are going to extend the front ends of our 883 and 1200 sportsters and am curious if going to a 6" over stock extension tube set will be too much. We have both already added a 3 degree raked kit to the bikes. Right off we noticed that the front fork clearance was shortened which is one of the reasons we are going to extnd the front ends, but 4" seems to little to make much of a difference and we want to make sure that we don't loose the smooth handling of the bike by going to a 6" extension. Also I was told that I should also replace the seals when replacing the tubes. Is there any special tools that we will need and any other parts that will need to be replaced (other than our heads LOL!)?
Thanks for your time.
Ed

Answer
remember, the farther you stretch the forks the better it will handle going in a straight line, but you will lose in turning. Going over 6" will be fine. the only thing is with 39mm forks, they will flex more extented, so I would add a fork brace.
As to special tools there is really none. You will need a metric allen wrench for the bolt in the bottom of the fork. Yes you shold change the seals in the forks. Better to be safe than sorry and have to do the work again.
Good luck and happy riding
Mike