In an Assembly, I'm trying to set two similar parts a set distance apart in space.  I want to mate them by the center of a hole in each part.  I can mate by distance using the origin of each part, but that's not where I want the set distance.  I've made axis through the hole  and planes through the axis, I thought an easy mate of distances between the planes, but mate won't recognize both planes at the same time.  That is, I can't set the mate distance between parallel planes through hole 1 and hole 2.  Nor by axis, nor by 'mate reference' point.

This seems a simple problem to me, but I can't make it work to do the simple set distance between the bottom holes as shown below.