I don't know how a Savannah is cut,but I doubt if it's cut deeper than my recurves.They are 50# and I tuned some 2016's and 2018's to them once.The shafts were 29.25".The 2016 took a 100 gr adapter and a 145 gr point and came out,573 grs.The 2018 took a 100 gr adapter and a 175 gr point and ended up,650 grs.
I later increased draw length so a 30" arrow would require less,up front weight.2216's are spined 20# heavier.
I would go back to the 2016's and play with a wide variety of field point weights till you find where it is TUNED.I would do no cutting or shaft changing till I found that spot.After that,you could make a change if you have to.
You made no mention of your draw length,arrow length or any type of tuning.If you haven't been able to get good flight with the 2016's yet,you will be swinging at windmills,changing to 85# shafts,on a suggestion.Good luck.