Alright, I figure a way to be able to fire the shutter right away instead of wasting several frames at the beginning. As 35mm film strip start much earlier than 120 film.
Basically once you make sure the film securely rotated in the spool, you turn the shutter count counter-clockwise to get pass 0, then close the door, and you can shoot right away once you cocked. (basically like you plan to dry fire the camera). I started out at counter 2, and after a shooting session today, the counter move as usual to 10.
Will try to finish the roll and post some result. I use the 45mm today but will use 105mm for the remaining shots.
The fit is, quite tight and the 35mm film canister did not wobble inside the tray, The two fitting "nuts" are different sizes, and if you put them wrongly in the canister, it will wobble. Will show a picture tonight. Oh, I end up did not use the framing as well, as I am afraid it will affect the metering...
Pic showing the fitting, pretty tight, I folded the tip of the film strip, since 120 film usually have one to help roll on the spool:
Here is how it roll to the spool, got to make sure the film is not tilted, as you can see, I don't want to use the frame, for I wanted the sprocket holes area to expose as well, and also don't want to mess with the curtain: