Here's an idea ...
Create a new variable in your Pass-In Fields and call it "NoneCounter". Define it as a whole number.
I'm making a few assumptions here. Assume 10 conjoint pages (Q1-Q10) are displayed. Also assume your "None" code is defined as code 5. After the 10 conjoint pages have been answered, pop this Perl script into the footer of the next page ...
[%Begin Unverified Perl
for($i=1; $i<=10; $i++)
The NoneCounter variable counts the number of "None" selections across the 10 pages. Within your skip condition, use the condition "NoneCounter<8". I just gave it a test drive and it works a treat.