The nature of any material you inject into the penis for that purpose is that it’s going to be flexible, otherwise you’d have a permanently hard penis. Since it’s soft and flexible, and it isn’t going to harden in response to arousal like the rest of the area; you’ll have a hard tube with soft stuff around it. I sort of picture a raw chicken drumstick sort of texture…
It might measure as a larger girth, but it won’t feel much bigger when it’s inside someone else.
I recommend exhausting other possibilities, like the activities talked about on here or options like PRP injections, before resorting to injected thickeners.