Hi Mike, Welcome to Tradgang!
This forum is intended for questions about how to shoot the bow. Questions about equipment, including arrow spine, belong in the Powwow forum. Maybe a moderator will move your question over there.
I typically shoot .600 spine carbons with a similar setup to yours, but with 100 or 75 grain points. I usually don't shoot aluminum, but 1816's with 100 grain points seem to work pretty well. 1916’s aren't out of the question, particularly if you're using 125 grain points. Occasionally a person might get a false weak response, meaning the arrow is really too stiff, but is rebounding off the strike plate and so showing a false weak. But if your 2016’s are flying well, I doubt that is happening here.
I assume your arrow is properly aligned just outside the centerline of the bow?
For a bow pulling 37#, I would imagine you are looking for an arrow that is as light as possible in order to maximize performance, rather than something heavier to hunt with? I have friends who shoot bows in that weight range who shoot .800 spine arrows with probably a 50 or 75 grain point.