Ive done a ton of tinkering over the past 2 years with my arrow set up and have finally found a set up that is super tune-able and so far any broad head I've screwed on has flown just like my field tips. Im far from an expert and Im still trying to learn, just wanted to share what has made a huge difference for me because its made me more confident than I have ever been with a broadhead on the end of my arrow.
Re-reading RadSav's posts and listening to Aron Synder's podcast is what led me to keep playing with set ups until I found one my bow liked.
First, I was under spined with my previous set ups. I was worried about having too stiff of an arrow that wouldnt be forgiving or so I thought. From what I've experienced, its better to have a stiffer spine that you can then "weaken" by adding point weight or inserts. Spine charts that manufactures put out are good to a point but I didnt consider that a spine chart doesnt take into account the rest of your arrow components.
I messed with various broadhead and field point weights and swapped brass insert weights in and out. It blew my mind how much a heavier arrow up front (brass insert and a heavier head) tightened up my groups, improved my arrow flight consistency and improved fixed blade broadhead flight.
I got to the point were I made my arrow too heavy for my preferences and my shots at greater distances started to diminish so I backed off a little weight.
I'm currently shooting 100gr tips, 75 grain brass inserts on my black eagle spartan 300's and Im having great results. I shot Muzzy 3 blades, Rad Ticon 100's and G5 Montecs Sunday afternoon to test them out and the groups were pretty dang tight. I've also shot Stinger buzzcuts and they flew well but I didnt test those on Sunday.
Two years ago I would have just put on 100 grain broad heads, adjusted my sight to account for my broad heads hitting right and high and called it good. I'd pull arrows of my target and they would be a different angles which only hurts the confidence.
Just wanted to share my

as hunting season gets close. Im still tinkering and hope to fine tune everything even more but something as simple as adding point weight and shooting a heavier arrow can make a huge difference in the flight of your arrow with a broadhead.