Just one more piece(s) of advice. A skinny striing can change yur tuning, noot likely if you are already shooting a ff string, unless you are close to being out of tune already, which unlless yoour release is perfec every single time, you would know shoting a 7.6 gpp arrow. If it does, you already got the orginal, so you can always change back.
Swiching to the heavier head may change your spine, but I doubt it. Carbons juust shoot anything most of the time if yu have the proper trim for your setup. Being you are long drawed, your shaft is likely spined in the 55-75 range to get it long enough to be able to pull. So once again, a heavier head can't hurt because it will be much more likely not to change your spine versus doing so because they have that designation for a reason. They are very tolerant and accurate to designation when left 28 inches or longer.
But once again, if not, you can always go back to the heads you have use the new ones next year because one thing for certain, if you change nothiing but one thing, it beter be to get a heavier arrow. And head weight, weight tubes, or inserts are required in almost all carbon setups to reach desired weights, No loss possible.
String stretch could be an issue if you buy the wrong string. It won't be if you buy the one preconditioned and made of thhe best material no to. 5 minutes of form work should settle a properly made and conditioned string. At least in my expierence. No loss. It is the best investment anyone could make to quieten a bow. No stretch equals no noise or vibration. Win, Win for you in all categories.
The silencers, I am not sure how to respond to that because I have never gave it a thought and thank the Lord I have never had to. As far as he 2 week claim, it could be correct. Depends on your striing material now. But goodness, if it don't work just put the old stuff back in action. No time lost.
Sight pic? I shoot 7-11 gpp arrows at hunting ranges routinely. The only impact difference between the two is 0-10 yards and beyond 40. The first is going to be an inch or so with the heavier arrow hitting higher at karate range, the second might show a lite more drop off with the heavier arrow but, lets face it, a few minutes of shooting will reprogram everything need be to offset either of these extremes.
But more than anything, you got the old stuff, just chage it back until after season if it doesn't work. What is too lose? God Bless