I agree.
My comment was related to ease of integration though. If you don't plug the port, integration will be more difficult, so measurement will be a must. And even if you do integrate via measurement, crossing over close to the port tuning frequency (less than an octave if you cross at 50Hz) will be hard work.
I'd consider a higher XO frequency if I were you, more like 80Hz, for easier integration and less stress on the mains. But I know others here may disagree with me.
So I experimented with both high-passing the mains and plugging the port, as well as adding 3 ms delay to the mains. I picked 53 Hz as a starting point because that's the F3 of the mains with the port plugged.
The good:
The subs and mains blended well. There is room for further fiddling, I'm sure, but the blending was pretty seamless.
The bad:
Plugging the ports over-damped the mid-woofer dramatically, crushing the dynamics and affecting the imaging and midrange in a bad way. The Contour 20 is pretty neutral / lean even with the ports open (maybe a bass alignment Q of .7), so plugging the port may have pushed things to .5 or even lower.
Taking the plugs out, but keeping the high pass (53 Hz) improved things dramatically and mostly sounded better than with no high pass and/or no sub.
It was an interesting exercise in "textbook generic" vs specific implementations.
The next step might be to leave the ports open and move the HP XO higher, so it's at least an octave above the port (>64 Hz).