I stand corrected.
I thought you were saying that Halcyon's aluminum plate was stiffer than others. The bends in the plate are going to create a structure that is stiff from top to bottom. All aluminum plates are going to be comparable in that regard......I thought someone had told you the 'H' plate was stiffer.
I'll be ordering a DSS kydex plate soon with a doubles rig. It looks from the pictures I've seen that there is a stainless center section riveted to the kydex. It would seem that they would be just as stiff along the top to bottom axis.
I have never used or seen a DSS kydex plate so I am not sure. I'll find out soon enough.
As for Halcyon, I like their backplates and wings too
.