It seems you have it under control, and understand them well.
Like G- said, real resting voltage displayed on our "tester" shows 1.42 at full test , I've seen the unit push them up to 1.47 during deep or Prime tests, but not any have I seen them pushed to 1.8V, at that point they'll be venting, especially the NiMh ones as they generate more heat as they charge then NiCds normally do.
The neat thing is that with your sweep meters, you can actually see when the longer period of max voltage is coming up.
When they are depleated and you insert them into the charger, as you noticed they take the full 800mA when they reach 1/2 full then the chemistry comes into play and forces them to not be able to charge as quickly, each time they get 1/2 fuller they will normally cause the incoming current to drop by 1/2, unless of course your setup allows it to be overcome.
This is where heating and venting comes into play.
They can safely take a full 1C but with your arrangement a timer should be fine, also since this is an open air charging you can get away with higher charging versus in-device charging. You should get more than 500 full cycles charging with this setup.
Any broken lawn light around? they're great for finding those pesky diodes
Keep Smiling;
Bruce S