no prob ...but you did loose me with the (IFS) i sorta got what you ment about 1.5 inch insted of 2.5?
The conversion is more related to the strut placement on the lower control arm than being IFS.
If you look at a vehicle with coil over strut (Mcphearson strut) as found on most front drive cars, you will note the strut is attached directly to the spindle knuckle.
So, the strut movement to spindle movement is one to one.
On a vehicle with a modified Mcphearson strut (means has upper/lower control arms and strut experiences no side load or has nothing to do with caster or camber settings) such as our Commanders, you will note the strut attached to the control arm at its approximate mid-point between frame mount and ball joint.
When the static length of the assembled strut is increased through the use of a spacer, say 1/2 inch, the ball joint will have been repositioned almost 1 full inch.
Now, as the lower control arm angle drops below the center point of the attachment at the frame, the difference at the ball joint becomes less.
For example- The first 1/4" results in 1/2" at the ball joint.
The next 1/4" results in about 7/16ths at the joint.
The next 1/4" results in about 5/16ths at the joint.
Hope I didn't muddy the water too much there,