Did you check your brace height, and what is the string material? I make my strings out of b55, after I stretch them it still takes quite a few shots to get the string where it needs to be. I’ve never used fast flight so I don’t know if it stretches at all or just significantly less.
It looks like its the same material. 14 strand dacron bow string.. Brace height is measured the same. Maybe just needs more shooting and days to 'stretch'? First time changing out the bow string.
I would think so. I takes my bows 40-50 shots before I quit playing with the brace height. After I get my initial bh measurement I don’t measure it again until I have quite a few arrows through it. I adjust the string a turn or half turn a time. That’s what works for me.