Circus 2 - there is a quicker way to do it.
Circus 3 - definitely a backroute, albeit a very clever one.
Circus 4 - I've seen a few backroutes around the exit, but they all have a bit too much precision. (it's kinda hard to prevent them though)
Circus 5 - I kinda like both routes, but the alternative one (which you did) does leave the cannon bit until last, which is a no-no unless you have huge amounts of time. Not sure if I should block one off or not.
Circus 6 - ballooning over the pit is a lot easier than up through a laser hole
(and still not the intended route - but again, as you mentioned earlier, these levels are more open-ended)
Circus 7 - one of my favourite puzzles. The reason I add so many twisters (unless it breaks the level) is because they're so unreliable and fiddly to use.
Circus 8 - oh dear, that's embarrassing...
(can be easily fixed though)
Circus 9 - another backroute, but can also be fixed.