Agree that Car Dropkick is a bit of a tricky one to clip together. Helicopter Dropkick is a very enjoyable figure to flip between modes [but people's mileage may vary]. Jet Shatter manages to both be very nice and intuitive and very basic at the same time. Winner of Studio Series for me is Shadow Raider/Lockdown. A transformation you can do in under a minute and imposing in either mode. But yeah I think some of them may be a bit overengineered for their size/parts count.