First, I added a structural blob to hold everything together.
Keeping the cannon centered on the arm was trickier than one might suppose.
Inside of the arm needs some love too.
I started trying to sculpt matching plates on the top of the join. That's when I found out how much sculpting practice I need.
Starting to try to match the contours of the existing lumps, plus added a couple of tentacle-hose thingies for fun
Not too shabby, for a simple kitbash...