Superb photography! As for the 'holes', they have sometimes been given the informal name 'lacunosus'. Sometimes, such small holes may appear, but I suspect that in the main, these features are actually more like mammatus. You can see a detailed image of very similar features at about 2m12s into this BBC audio slideshow made from my images back in 2010:
The pictures are great. I'm very interested in the holes you report. I've been chasing these for a while. If you look back through some of the older general nlc posts you'll find out more about this occurence. (Top of page 4, Jul 30 2008.) I had a vague impression of them here last night too but there was too much high cloud for me to be sure.
If you look at the short video on youtube I posted from last weekend (http://www.youtube.com/watch?v=I26xnuxUtVE) with the nlc near overhead you can see a more open "holey" structure.
This may or may not be the same type of structure as seen from a better viewing angle but the video shows lacanosus by definition of the holey or net structure. If it is the same sort of thing it doesn't look like mamatus, at least to me.
However keeping an open mind I'd like to hear more about the mamatus idea. What's the thinking?
Upon studying your pictures a bit more closely it's surprising how similar they are to the one I put up in 2008. With the holes forming around a distinct dense twisted feature. Excellent stuff!
If you see these again, experiment with a range exposures (even if you over expose other parts of the clouds) to try and get a nice bright image of the holes and the immediate surroundings. good hunting. Bill.