Tim,
I've use a 9.4 Beal combined with an 8.5 half rope...seemed to work pretty well...Regarding Fern's comment, we set up to pull the fat rope, not the thin rope...
the beauty of using the half, is, if need be one has the option of actually using it as a half rope for a wander pitch or two...or if the main rope gets stuck or otherwise compromised, you can double the skinny and lead up to clean the stuckage (haven't had to use this)...a static tag loses these options for the same weight...plus, i presume you already have doubles or halfs for ice??
my worthless 2 cents...don't climb anymore so take it for what its worth...