Northstar, have you tried using Mask All, adjusting the Select Count and Skip Count sliders, clicking Columns and then HidePts? This is what I got using those, dont know if it will work the same with your model, worth a try though…
It’s the ultra powerful of the operations of masking!
Pilou
Northstarr - have you tried with just the basic objects ie. does it work as expected with just a sphere ? Using the ctrl drag method I’ve got some strange results when I forgot to “lock” the object to one of the 90deg positions (ie shift rotate) and also if I do not use the “solid alpha”.
Hi Nocturnal
have you remark if you turn the volume who has points hidden, the section “stay open” even “double” is On !
Not visible here because you have turn the volume ! 
How resolve you this problem ?
Pilou