Well that ain't enough weight really for a DH outfit. I have a Steelfin XFR which is heavy but doesn't hold enough line, which is, if you are using floating or intermediate heads just too thick and occupies too much space on a LA reel. I think you need to go for a different system, like a deeper arbor, and larger no hole reels to get more weight.
I'm using fly rods off ocean rocks and you need a large length of backing, like 500 yards minimum, plus a 120 foot running line and a 54 foot sinking head. The reel has to hold that lot and not get jammed up.
You can't have your GsP backing off the reel because its too prone to problems during casting, and you need some shooting line around the spool, a chunk, depending on rod length up the runners and around 80 feet out on the cast, to get a decent distance, also depending on the rod length and rating.
The outfit has to balance and that means the reel size and weight is critical and specific to the rod length. A reel that balances a 12'6" 9# isn't going to get near a 15' 10/11.
Cheers Max