Problem selecting light grey.

[TrevorW]

I have been wrestling with a selection issue.  Funnily it is something I used creatively in PS but in SAPhoto I can't get round it.  I recently took a photo of Lincoln cathedral.  Its pinnacles are covered in light grey lead.  I selected the sky (uniform light grey) and then refine edge to sort out the trees, small pinnacled and balustrades.   The pinnacle tones are similar to sky so I was not surprised to find the programme struggling to select these easily.  I painstakingly painted in the shapes within refine edge.  Marching ants were in the correct place.  However when I used the mask I found that even though I had noticed the red matte of refine edge was somewhat pale and painted in to be deep red, the mask was 50% or so transparent.  The sky replacement obliterated much of the selected pinnacled.  I tried using the pen tool to make selections (my preferred option in PS) and tested - no luck, still partially transparent and indeed when I used refine edge to add to the density of the mask by painting in the selection, it even began to bleed outside the pen selection areas.  

Anyone got a solution, please?