tensioned ballscrew

I have two ideas that need to be challenged. The screws on the X axis of my
router are ten feet long. They are 1" diameter, .25 pitch from Rockford.

1. We have come up with a way to provide intermediate support so as to get
around critical frequency problems. An extra pair of blocks on each linear
rail will carry support bushings. These blocks are connected to each other
through a beam about five feet long. This beam is tied to the gantry
through a 2:1 cable arrangement so that the support blocks move at half the
speed of the gantry. Thus, the worst case support is when the gantry is at
one end and one support block is in the middle of the screw.

2. Now for the end bearing blocks. I want to use a tapered roller bearing
at each end of the screw and tension the screw between them. This poses two
possible advantages. First, by tensioning the screw I can further raise the
critical velocity (though I've been out of college too long to remember how
to calculate just how much). Second, by varying the tension in the screw I
should be able to adjust out any first order pitch error (though not second
order or cyclic errors).

Of course it would be best to have two bearings at each end of the screw, so
I propose putting a regular ball bearing about two inches outboard of each
tapered bearing in the bearing block. This would take up radial loading and
thus improve end fixity of the screw.

I welcome y'alls opinions.

Doug