what would be a good starting arrow weight for a 45lb longbow?

Depends on your draw length. 1916's or 2013's are a good start. 1916's if your draw length is under and up to 28 inches and 2013's if it's over.

I shoot a 45# (at 28") recurve, but pull 30 1/2".  2018's fly great for me.  Don't know where Jenison is, but if you're close to Clarkston, I have quite a few arrows in the size range that you should try.  PM me if you'd like to get together and try some out.

we shoot at west walker sportsmans club every sunday @6:00 pm if you want to try some arrows. i have some 2018's that might work. west walker aint too far from you.