In all seriousness I use Black Eagle and only way I'm switching is most likely to Grizzlystik offering BUT Sirius and their package of multiple spines and such to mess around with before a big order is literally screaming your name. I'd look into it.
Why not cut your 400s down by an 1.5 inches and put a fifty grain brass insert in and call it a day? Build three of them tune you bow and decide from that point, you most likely will be just fine.
This is what I would do. This had worked for me the last 4-5 bows/arrows. Get free trial (or buy) Pinwheel Shaft Selector. Use Axis 340. 50 gr insert the rest of you components (vane/nock/etc) Let the program tell you what length to cut them. As long as the BH is past your fingers. Took someone for stitches once. If not go up to 300. FWIW - In the 45+ years of archery I never had an issue with an over spined arrow, only underspined. I shoot the same Axis 300 from my #60 & #70 bow with zero issues.
My opinion if you opt with the Gold Tip shafts is to buy the 50gr weights that just screw into the back of the standard insert. Easy way to add some extra weight up front. I’m at about 460 gr total arrow weight and shoot Spitfire XXX broadheads. Have had zero complaints
I don't shoot Gold Tip but this is from their website. I use a similar system with the Black Eagles https://www.goldtip.com/Components/FACT-System/FACT-Weight-System.aspx
How much weight up front (insert, extra weight, field point) would that give you? I found with my arrows that I was good with 225 grains up front on a 300 spine, but, if I went heavier, I needed 250 spine.
You'll want to go to a 300 spine if you do a 50 grain insert. Adding weight to the front eats up spine quicker than you think. A 70 lbs draw with a 27" arrow on the GT calculator will show a 340 with a 100 grain head, but just changing it to a 125 head makes the calculator jump to a 300 spine. A mere 25 grains is enough to tip it. You want to run a 100 head, but do a 50 grain insert, so you would be another 25 grains heavier up front than that. I'm hunting with a 340 spine GT XT Hunter at 26.75" long. I have 12 grain inserts with 20 grain FACT weight in the back of them. When tuning (bareshaft at 20 yards), at about 67 lbs draw, I was seeing the arrow hitting nock left into the target every time with a 125 head. I switched to a 100 grain head before changing anything and suddenly the arrow was going in straight and matching my fletched arrows. I will do 300 spine next time I build hunting arrows.
Mine came out to 403 on a scale with a 100 grain head. But the XT's are 8.9 gpi. Kinetics are heavier, the 340's are 9.9 gpi and 300's are 10.4 gpi. I really wanted to run mine with a 125 head, but tuning showed I cut it too close with spine.
I am getting a couple different spines when I try to use a calculator. some say a 26.5" 340 with the 50 gr insert and 100 gr head some say 300 with same length and weight up front... I am leaning towards the 340s being that the 400s are shooting well. I like those GT xts. I believe if I run a 26.5" arrow and use those 50 gr inserts with 100 gr head I should be darn close to perfect. put me around 430 gr +/- however, I am pulling 72 lbs now.. so a bit more than you and they may make the difference..
