Can the bottle inside the Reo be filled by sticking a needle tip bottle
through the 510 connection so it just goes down the tube into the bottle?
That's an idea...something I've never seen asked here. I would say yes (I have an old goat
mod that has a needle (from the bottle) and it works well. The other direction- I would think it would work but you might want to unscrew the bottle a bit to give it some breathing room, otherwise, I can see a vapor lock situation happening and spilling up into the catch cup. What a concept!!!
buy one, try it and report back as to this method- I would be very interested to see if it works...just be careful not to puncture the feeding tube with the needle! Obvioulsy, you'll need to take the atty off when you do this. (my 2cents).