Thanks for all responses. I read through them all a second time to make sure I'm not missing anything.

A few people mentioned sealing the hinge line with covering. The Alpha40 instructions don't say to do this, but I understand that it is good for airflow (and maybe also for avoiding flutter). I don't have any extra covering of the right color. I suppose I could do this later (even after having done some flying)?

Also relating to the hinge sealing/gaps, the Alpha40 instructions does say to push the control surface all the way against the trailing edge after removing the pins and before adding CA (the control surface edges are slightly beveled of course). Does generously flexing the surface down (to drop in the CA) not ensure that there will be enough flexing in the hinge line (without deliberately leaving a larger gap)?

As for the hole in the centers of the hinge slots. I was thinking I'd make sure not to drill them any deeper than half of the length of the rectangular hole in the CA hinges. I figure that would be good since the hinges already have slightly less surface area because of the rectangular hole.

One last thing about this process that makes me a little curious is the time that elapses between doing the drops on one side and then the other. By the time you get to dropping CA into the other side, is the CA not already fully hardened making the hinges non-absorbing? I'm just seeking a better understanding of the physics of this.

Thanks for all the input