In reply to Pay Attention:
Thank you SophieG, GridNorth and HeMa for your considered replies. I appreciate the points you made.
I accept that distributing potential force of impact among all anchors will reduce the potential force on any one anchor. Realistically, all ice anchors appear equally safe when placed, otherwise you’d replace the weakest one, no?
A couple of days ago I had to set a hanging belay on the Spiral of Contingency. A pair of ice screws were equalised with a quad anchor for the main part of the belay. By the by, there were three other anchors as back-up.
The problem with the quad anchor is that it is static tape and creates a wide angle when fully deployed.
I’m thinking it would be better to set my main two ice screws vertically rather than laterally (as a vertical A-thread is considered preferable to a lateral V-thread).
To reduce belayer movement I’d tie my rope in to a focal point using the lower screw as a fixed anchor.
I fond the ACMG fixed point anchor video link I was referring to. Of course, it’s lateral not vertical, but you’ll get the picture.
At 03:52 it does say: “If the option exists, vertical placement works best”.