I measure 42" to center of spindles/knuckles. At the front tip measured them to just over 42" in the center groove, and then measured the back edge to a bolt on the tunnel(16 1/2") if I recall right. Doesn't matter what you use as measurement guideline as long as you can use the same reference point from side to side, and as long as the bars are straight, and your front & rear measurements are close the skis will be even. Took me a while to figure out mine, my wifes f5 was dead on from the dealer. As for her front end plastic, I have a lot of work to do to get that all evened out, worse than my F6 when I got it.
Pop cap off top of tie rod bolt, loosen lock nuts and tap them out gently with a hammer & small block of wood. Hardest part was keeping the tie rods in place while i took measurements. Could probably use a pair of vise grips fit loosely with a rag. Too much of a pain to keep running the nut on and off while I adjusted. Have to make sure tie rod is seated all the way in the knuckle, otherwise that alone can throw measurement off by a 1/4" or more. The inner part unlocks and turns also, which is what I did for some of the adjustment. Didn't want to have only a thread or two holding either end on. Once you have it, a small drop of loctite and tighten your lock nuts back down. Used a dab of silicone to hold the plastic caps back on(dried overnight)