match lines where a specified column range contains dot character and only print the line if the pattern is found 8 times or more
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I have a tab delimited file in which starting from columns 10-25 some of the values contain the "." character. I want to filter out lines which match the "." character, within this column column range,so that it does not print if it is found less than 8x times in columns 10-25 (i.e. less than 50% occurrence). 

I have tried looking at similar posts and the closest I got to is by the user: lodge (http://stackoverflow.com/questions/6005794/match-lines-with-pattern-n-times-in-the-same-line) however, when I tried some of the commands it doesn't behave in a way that I need to.

For example, the code below replaced everything with a dot...whilst I am aware it is because it is a global substitution, it seemed to work for lodge.

        awk '{ if (gsub(/./, ".") >= 8) print }' merged.vcf > test.vcf 