increase delay before output is parsed by phantomjs

hi,
as this
production.ERROR: PhantomJS - Invalid response
occured, I investigated with the test-phantomjs script.
When I use it with delay variable set to 0 then the complete page ist returned.
Increasing the render delay to 1 returns output starting with:
<head></head><body>data:application/pdf;base64
so this would be correct and works but application obviously doesnt wait and it cant be parsed.

so how to increase that delay?

thanks.

The relevant code is here:

https://github.com/invoiceninja/invoiceninja/blob/master/app/Libraries/CurlUtils.php