How to stack and phase dissimilar yagis with same type feed systems.

Here is a typical Question about stacking yagis with the same type feeding system. 

 
Hi Jay,
 
Question for you.
 
I am putting up a stack for 10m that consists of a homebrew 6-el at 90' and  two 4-el Cushcrafts at 60' and 30'. Feeding this through a WX0B Stackmatch.   All antennas are fed with a split element hairpin match.
 
Obviously the 10m has a much longer boom than the Cushcrafts so its  feedpoint is further out from the tower.
 
Do I just put equal lengths of feedline to them all and hope for the best? Is there some way to calculate if the 6-el needs a bit of extra feedline to  improve the overall phasing of the array?
 
Any insight or suggestion would be appreciated.
 

Simple and effective method:

Measure/calculate the difference in horizontal length between the mounted driven elements.

The one(s) that are "in front" of the other need to be delayed by the amount of time it takes the RF wave to align it self with them to become in phase. 

So a length of coax is cut to match this time amount, but you have to take into account the velocity factor of the coax. 

L = D X VF.

L, length of coax to add to the "leading driven element"
D, Distance in feet or meters between driven elements
VF, Velocity factor of coax

I will work on reducing the resolution of the pictures. I thought I had done that.

Thanks for the tip. I know I have some monster pictures on the site. That need to be reduced.

Jay