Jehnert XE200 woofers are 55mm deep, and they don't fit without a spacer. That Vifa has no prayer, I'm afraid.
I have not tried the CAW428. Since it's already 8 ohms, I would not even attempt it with a passive crossover. If I did use it with a passive crossover, I would design the crossover myself... but those Morels don't have great HF off-axis response (I like Morel a great deal, but they want their own low-Fs tweeter crossover points). I would go active if going that direction and I'd get the Vifa 25mm ring radiator if I had to. But with an 8-ohm mid and a 4-ohm tweeter you're gonna probably need a lot of attenuation in your passive (especially an on-axis 4-ohm tweeter) and that will take a lot of trial and error testing. As long as you're up for it. Use wirewound resistors if you can they sound better than the cheap sandstone resistors.
musicar northwest portland or musicarnw.com
Web site migration complete, still repairing problems. Sorry!