you have a Q3 right? are you willing to confirm by hanging 3 sack of 10kg rice on it to see if it droop?
like you, i used to think that since the Q3 can hold up to 30kg, why do i need other ballheads like the M10/M20?
first reason is.. i was told that the actual rated weight for Q3 is not 30kg.
secondly, the size of M10/20 are bigger compared to Q3. therefore better ratio and stability.
Try putting your setup with a 50mm prime, and tapping the ballhead lightly. Notice the camera movement. Then replace the 50 prime for your bigmos 50-500, and tap the ballhead again. You'll see that the camera will shake a lot more.
Even your BH able to support up to 30kg or 45kg.
still your tripod only able to support up to 8kg. (example : GT1541)
So even you have a BH able to support 45kg or 30kg.
but still you limited by the tripod load support.
In this case you have to upgrade to a better tripod able to support 45kg.
but so far I only saw GITZO tripod only able to support up to 18kg of load.
in this case... no mattter what kind of BH you have still limited to tripod.
Am I correct on that??
Sorry, I still very new.
I just base on the number from the tripod and BH support weight and come out with this conclusion.