don't re-invent the wheel:
Please look back through the Birdview related threads for some help.
I don't have all the details book marked, and can't remember everything, but...
I think it was Phlatwound who described how he used a hole saw to enlarge the scalar hole...
Others have taken the scalar to a machinist who used a hand grinder with a router-like tip (not a wheel) to open up the hole by hand.
Others have used a file, I believe.
You can spin it on a lathe to easily bore the hole to any size needed.
Check back through the threads for all the ideas that were tried.
Obviously some of the techniques are better than others.

Linuxman was probably the first one here to write extensively about Birdviews on the forum.
Might want to start with his.
And you are right, breaking the scalar support struts is a real possibility.
Stogie5150, and maybe Phlatwound have written extensively on the problem and the cures.