Newbie- Help with selecting acme thread and steppers

[esm]

I'm building my first cnc wood router. There are so many combinations of components to achieve the desired IPM. Help me sort through them, won't you?
This is to be a production router, fast. 100 ipm or better. I'll be cutting 3/4" ply.
*These are all my best guesses*
Acme Thread: 1/2" 10 TPI 2 Start
Gantry Weight: 50 lbs
Cutting force: 100 lbs
Motors: Need help here

Because of thread whip on a 96" unsupported acme screw, 308 RPM is max. does this mean I'm stuck with 60 IPM? Does the drive nut count as a support? A support that varies from 48" to 96" in unsupported lengths? As the nut moves toward center will it tame thread whip?
Ideas/suggestions? Maybe this is where people start looking at rack and pinion.

I've been reading:
Mariss Freimanis post #10

[ger21]

The link you have there isn't 1/2-10 2 start, it's 1/2-10 5 start. Regardless, it's too small for a 96" screw.

What size is your machine? What are you using for a spindle? 100ipm is very slow for an 8' machine cutting plywood. Fast would be 1000ipm. And 50lbs is awfully light for a gantry on an 8ft machine. Need more info on the machine. What kind of plywood and what thickness will you be cutting?

[esm]

oh, right.....the size of the machine....
Cutting Area: 49" x 97"
Spindle: 3.25 Peak HP Porter Cable Router
Cutting mainly 3/4" CDX and 1/2" OSB

1000 IPM is definitely fast. It would be great but I don't expect to even get close.
I'll post my CAD pics as soon as I get home tonight.
This process is like trying to figure out whether or not the chicken got the cart before the horse or did the egg beat her to it.

You are quick, thank you

[esm]

Lets try some jpeg screen shots.

The base of the machine will be 1.5" X 3" .125 Steel
3/4" MDF as sacrificial substrate.
Gantry will be 3/4" Birch Ply.
Linear rails are 1/2" ID sch 40 pipe
Linear glides are ABEC 7 skate bearings bolted to a steel "L"

After rethinking my gantry weight, you're right ger21.
Maybe 200 lbs for the gantry would be more realistic.

What else am I missing?