I've recently started making my alpine (or "trad") draws by girth hitching one end of a sling to the gear side carabiner and then clipping and passing the rope side through as usual. The girth hitch makes it easy to lengthen the draw one handed as all you need to do is unclip the two loose loops from the gear side carabiner and the sling will lengthen automagically.
Its a technique I learned from a german mountain/climbing guide friend of mine. Personally I think it's a lot easier to lengthen the sling than the standard way of making alpine draws. The knot reduced the runner rating in half, but since there are two strands , its back to the UIAA standard of 22KN, well above any forces seen in lead falls on intermediate pro (not to mention the ratings on the pro itself).
On a recent trip a climbing partner pointed out that the girth hitch can induce horizontal forces on the carabiner, and if the hitch slips "up" the carbiner it can even load the gate and slide off. Which got me to reexamine my alpine draw technique.
Just to demonstrate, (not my image), the way a girth hitch looks on the biner. The two loops have a slight tendency to slide up the two sides of the biner if the knot isn't loaded/tightened (I make sure to give it a yank when placing).
So is what I'm doing bad or known to be wrong? I trust my guide friend, but maybe I should pass on this particular tip?