Link Length question?

So I'm setting up my watts link and I need to know the ideal length to make the links. THe inside off my frame rails are 28.5 inches apart. (63 chevy truck) The bolts for the links on the center pivot arm are 8.5 inches apart center to center ( I don't want the pivot taller than the pumpkin or it'll stick out of the floor). I think I understand about the link being only straight at 1/4 and 3/4 travel and the bars need to be even at ride height. How do I figure out the length of the links so I have the right angle of the pivot at he right time during it's travel. I haven't put any tabs or brackets on the frome yet so I guess I need length from center of each mounting point and then I can make my links to compensate for the heim joints if that makes sense. Thanks for the help.

Man I figured Max or Seth or somebody would have looked at this already. Everybody must be busy makin money. I'm a High School teacher so I'm on summer vacation and have more time than most to play on the computer. I Additional info. The truck is back halfed with 3x3 rails (no notch)like below, and running the stock truck arm setup. I can make the mounts any place I need to to get em in the right spot. Also I looked back at some stuff and I've seen stuff that says links parallel at ride height and others say parallel at 1/2 travel. Which is it? Last thing. Is there an ideal angle the pivot should be at when the links are parallel? If so I can figure my link length based on that. Thanks again for any help.
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I have been trying to push the "half travel" thing over "ride height" for some time now, but it only seems to have cought on to a few folks that genuinely "get it." I say half travel because every suspension has geometric changes through it's travel and if you do your best to set everything up as perfect as possible at half travel, then the suspension geometry only changes half of what it would over it's full travel. If you set everything up at "ride height" what consistency is there to how the geometry will all end up when the suspension is all the way up or all the way down?

On a properly set up Watts link, both bars will be parallel to the ground a half travel, but the center-link itself will be over-center. The center link will be straight up and down only at 1/4 and 3/4 travel. Also because there are 2 bars limiting movement, the links need only be half as strong as a pannard bar. It

^ perfectly put

It does get a ton of lift since the truckarms are so long and the bag is forward of the stock mount. I think I've got a pretty good handle on it but just wanted to know if there was an "Ideal" set-up to shoot for. Thanks again for the help.