Hmmm.
Take the weight or the radome unit, and multiply it by the number of feet to the waterline. Subtract from the keel ballast.
I'll leave it to a real engineer to get into the additional loading on the spar, and the effect of the windage up there.

I pulled some pretty nifty pieces off a beached piece of salvage not too long ago. Didn't keep good searoom in the fog, as his radar was bravely showing him the way...until it crapped out.

Not shy with my opinions!
Dave