I wouldn't mind a heavy arrow for elk, but I am new at this and haven't had the time to tinker much yet. my arrow CE hert 250 has about a 16.5 FOC at 550grs and about 40 ft lbs energy according to stu millers calculator.
To get up to a 650gr arrow I would need to do a combination of: getting a stiffer shaft, internal footing, and/or building up my side plate.
Since I have only been at this for less than a month I figure I shouldn't worry too much about this yet until I get my shooting form down.