I am a little surprised the 5575 works for you now if your bow is over 1/8” out from center including the strike plate. I would have thought it would be stiff. You may just want to try a longer 5575 with sufficient point weight to keep your GPP up in a safe area just to see what happens. This would be easy to do if you have any spare full lengths shafts in stock.
Assuming you are well tuned with what you have now, you will needs something stiffer to keep weight up. With 60# bow you will be less than 10 gpp with your current arrow and much less if you try and drop front end weight to offset the increased draw weight and arrow length. You will probably have to go to a 7595 in the GT, but those will be real stiff at 300 spine.
The CX250 could be a good option as it is less stiff than 7595 and about the same gpi if I recall correctly. The 250 is a little stiffer than the 5575 and heavier so you can make up some needed weight without having to go way stiff and way heavy on points. If that will not quite make it, the 350 is stiffer yet, but still not as stiff as the 7595.
The AD trad is a great one if you have the funds.