Hi,
Even if the borescope can't bend to see the squirter you could add a little mirror on the end. I'm quite sure that would be possible and the cost of a oil return line is peanuts in the engine build comparison. One guy at work have this model;
http://www.uniqueproductsonline.com/opticscope.html
Quite good and I think with a dentist mirror you would be able to see something.
Michael