Well, that bow was offered with 2 different limb options

Option 1: XT2000 limbs
This is the higher performance option (IBO 310)
With this setup a .400 spine arrow with a 100gr point and 28" length is a little on the underspined side
I would probably say that it is safe to shoot, but certainly not the optimum setup. I would look for something else.

A better option might be to either back your weight down to 62# where they would spine perfectly
OR
Go with a .340 spined arrow at 29.5"
OR
Use a .340 spined arrow at 28.5" with a 125gr tip (this spines dead center for your setup)

Option 2: ZR200 limbs
Slightly lower performance than the XT2000 limbs (IBO 300)

A .400 spined arrow at 28" wiht a 100gr tip will spine almost perfectly with a 64# draw weight (just a hair on the weak side but still right in the center)
If you go to the .340 spined arrow, you are probably looking at something similar ot the XT2000 limb setup (29.5" wiht a 100gr tip). This arrow spines just a touch on the stiff side, but still well within the shootable range.
The heavier tip option would be the .340 spined arrow at 29" with a 125gr tip (this spines dead center for your setup)


You seem to be smack in the middle between a .400 spine and a .340 spine
I would say that for a 28" arrow with a 100gr tip, an arrow that spines at .385 or there abouts would be a perfect fit for this rig.

Hope this helps.