Hi Peter, I was up on Stob Coire Bhealaich yesterday on my way up to Aonach Beag/Mor.
Here are a few snaps of the conditions which show some hefty cornicing where you want to descend. There is an abseil anchor point at SCB's edge which is used by ice climbers, but from what I could tell, it appears to drop you down slightly north of the connecting ridge you want for Sgurr Choinnich Beag/Mor.
I didn't go up to the edge of Coire a Bhuic (1st pic) so can't say for sure, but I think it might be easier to drop down from here then tack NE onto the connecting ridge.
I'd recommend taking a lengthy rope, technical axes and ice screws if you're planning on using the abseil post.
Hope this helps.
View over to Sgurr a' Bhuic from south slope of Stob Coire Bhealaich.
Stob Coire Bhealaich with Sgurr Choinnich Beag and Mor beyond.
View NW to Aonach Beag showing cornicing.