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.
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