Can you test it on the outside before installing? I think it will be pretty similar inside or outside, and that will give you a general idea.
Also I don't know this particular pickup and am not generally a fan of transducer pickups, but I do have some experience with them and think you're smart to look for the sweet spot as you put it. I think that it's generally safe to say if you put it by the bass side it will favor those strings and vice versa. Also if it's too far from the bridge output might suffer but too close and it gets a bad case of the dreaded piezo quack. Probably the only way to be sure you're getting the most out of it is to experiment.
2013 Angel Benito Aguado
2005 Ramirez R-2