I know this may sound insane. But yeah, I did it.
Have heavily invested in Canon gears already, but after found the reachability of Q7 and full-frame lens combo, I was sold.
After reading some related threads in this forum and learnt a lot, I think it is my turn to share my finding and hopefully it will benefit some other members if there is any in the same boat
Both shots were taken with Q7+Canon EF 70-200 f2.8 II lens at 200 mm, from about 10 feet away (maybe more than that). Used a tripod and a remote trigger. I think I might have stopped down to F4 in one of the shot, but I might be wrong.
Adapter: Fotodiox Lens Mount Adapter, Canon EOS Lens to Pentax Q-Series Camera, fits Pentax Q Mirrorless Cameras, bought from amazon.
Modification: At first, I painted the interior of the adapter with Rust-Oleum American Accents Ultra Cover 2x, Flat Black, bought from walmart. But it seems the result was not as good as I expected, and some light reflection was still there. So I tried a second method mentioned by a member (sorry, I don't remember his/her name), which is using felt tape. I didn't get the felt tape, but got some friction tape instead, from walmart. and the result turns out to be very good, at least to me, I'm fully satisfied.
Aperture control: bought a Canon EOS 2000D from ebay for $17 with batteries (man, the camera body is cheap, but the batteries are expensive!) Not very convenient though, I can still leave with it.
Shooting experience: had been shooting in the sun for about 30 mins, then the camera was overheated and simply started showing the thermometer symbol only... My wife was joking that I should have brought an umbrella with me... Focusing on the tiny LCD screen was tough. The magnified manual focus feature helps a lot!
That's pretty much it. Thanks for looking!