Snapping dimensions to blocks in layout/paperspace

Hello all,

I am trying to dimension drawings in a viewport in Layout. My dimensions would obviously be in Layout and not in Model Space. It is a simple matter of snapping dimension lines to individual entities, but if I want to dimension specific details of a block, snaps do not seem to work. Am I missing something here or are you unable to snap to blocks for dimensioning purposes in Layout?

I have a library of blocks that I have created that I use frequently in drawings, it seems strange to me that I wouldn't be able to dimension to a block in Layout without exploding it (which works but is unacceptable).