Heavy arrow from compound
 

To each his own TX. But there is a line of diminishing returns when you go to a heavy arrow. I shoot a 420 gr carbon Gold tip which includes a 100 grain tip at right about 300 fps. Everything I've shot with that combination was a complete pass through including 2 bison. IMO any heavier an arrow will just be slower.
I'm not sure how much knowledge you have regarding archery principles but if you go too heavy up front you're going to have to go to a heavier spine arrow. Too much weight up front with a weaker spine will cause your arrow to flex excessively which would very likely give you erratic flight. The Grizzly's taper may help.
If that's the route you want to go, go to your local shop and see if you can purchase a couple heavy shafts or fletched ones with the heavy inserts. Then try shooting your Grizzlys with both those and your present arrows.
Good luck