Cross-loading a carabiner over an edge will dramatically reduce its strength and is to be avoided. They are designed to be loaded along their major axis, namely end to end, with the gate closed. In practice, to avoid loading a carabiner across its back often simply requires using a different length quickdraw/sling extender. The extendable sling on the Dragon Cams and Torque Nuts are are ideally suited for this purpose.
However, in the case of when the end of a wired Wallnut for example is close to an edge, perhaps as in a horizontal placement, then this isn't possible. Here, to manage the edge, you could improvise by using a lark's foot (girth hitch) or a basket hitch to attach a sling, but which is best in minimising any strength loss?
To answer this question we took a Wallnut 1 and 11 and tested them with a sling attached using a lark's foot and a basket hitch in combination with 8 mm Dyneema (Dynatec), 11 mm Dyneema and 16 mm Nylon slings. We also tested lark's footing a Wallnut 1 together with another Walnut 1.
The results (see table below) were conclusive in showing that basket hitching is the best way of extending a wire over an edge to protect your carabiner. Using a basket hitch with the Wallnut 11 always failed above the nut's minimum strength rating of 12 kN. The same was true using a basket hitch with a Wallnut 1 having a minimum strength rating of 7 kN.
Note: These are best case results carried out under dry conditions and ambient room temperature using new products. The improvisations shown here are outside of recommended use.