Will my foxy go the distance?

Now that the lovely business of Christmas is over (well, it is in Melbourne!), I can turn my attention to lace. I have so admired the lovely work showcased here at the VLT blog. Something to work towards.

I love lace knitting and have completed a couple of simple projects (Forest Canopy Shawl, Birch Shawl, currently on Seraphim). I want to choose an "easy" pattern from VLT, as I have never done a knitted-on border.

The "Large rectangle with center diamond pattern" on page 20 most appeals to me. I have some Cherry Tree Hill cascade fingering 100% silk in "foxy lady". (This is good, cos I could so use some foxy right now - get me in the mood for the new year).

There are two things I've been thinking about:

1. Is 100% silk a good sub for kidsilk haze?
It is a fine weight, but the drape will be different. Does it suit the pattern?

2. The foxy yarn is 666yds. The pattern calls for 750 yards. Is there a simple way to calculate how much I need to reduce the length and/or width of the shawl? Would losing one repeat in the center panel (width) and two repeats of the ten row chart (length) be enough?

Any thoughts would be warmly welcomed.