I use the inner tubes for the EXACT same type of form as you, so it's not about the form. I think you're thinking of the forms with pegs etc.
Sure you can get good glue lines with that method but it's not as easy to get a good glue line as it is with inner tubes. I was just stating my personal preferences having tried many methods. The blocks and rubber bands take too long, and don't give as good results for ME.
I know Justin Snyder over on PA uses that method, that's where I stole the idea from myself and he sure makes some nice bows with that method.