Here's an overview of the atty feed and a few pics.
Take the bottle mod and measure the length of the bottle against the length of the 901 atty.
You'll want to match the two so the top of the atty is at least to the top of the lid so the drip tip will fit.
Make sure the bottom of the bottle is as flat as possible. Since the old air hole will be covered by the bottom gasket you'll have to drill a new one farther up the tube. Drill the hole close to top fo the gasket with the 901 in place so it will feed as the juice level gets low in the bottle. I used a 5/64" drill for all of mine. If you use thicker or thinner juice you might have to drill a smaller or larger hole.
Using the same bottom gasket, make sure the atty is a snug fit with the 901 in place. The top part is done.
The collector tank is the real build on this mod. Since the atty's air hole is now a juice feed, air will have to come from another source.....through the center hole in the atty connector.
Take an old carto tube and cut it to the length you want....it's not critical; I like to keep it as short as I can so the entire length won't be so long. After cutting the tube, prep both ends to receive a 510 atty connector and a 901 battery connector. Cut a slot in the side of the tube so air can come in there and up the tube to the atty in the top portion. Here's where experience comes into play. Cut it large and the draw will be loose; smaller and less air comes in so the draw is tighter. The tighter the draw the more juice gets pulled into the atty. I'd copy what I did and then you can adjust to suit how you like it later.
Solder a wire onto the center post of the 901 connector making sure you dont' block the hole....air has to travel up through it. Next, flow solder into the two air holes on the side of the 510 connector. Press both connectors firmly into the tube with the red wire feeding through the center of the 510 connector. Now solder the wire and seal the hole in the 510 connector. The 510 connector is now completely sealed so no air or juice can come in or out.
Take a 12ml syringe and cut a piece the length of the collector tank tube, making sure the ends are flat and level. Take a 1/2" or larger OD flat rubber gasket and grind out the center hole until it's larger than the diameter of the 901 connector. The hole size isn't important because the only purpose this gasket serves is to seal the top mod to the collector tank when you screw the two together. Using a 1/2" gasket, grind out the center hole until you can fit the collector tank tube snugly into the piece of syringe.
With the large flat gasket between the two pieces, screw the collector tank to the atty in the bottle mod.
It's important you seal the two pieces as tightly as you can so you control the amount of air that is fed into the top portion. If the two are sealed, you can make adjustments to the collector tank tube or more likely the atty juice feed hole.
Any excess juice will flow down the center of the atty into the collector tank...that's why I haven't experienced flooding. It doesn't matter that some of the juice gets into the tank because the 510 connector is fully sealed. IOW, the juice isn't going anywhere and there's nothing it can hurt by being there.
Fill the bottle mod and screw on the top. Insert the drip tip and you're ready to vape. If you draw too fast and it gets lean, just unscrew the cap until the air equalizes and juice will be pulled into the atty. Tighten the lid and you're back in business.
That's it. It's not perfect; nor will it ever be perfect.
This version is much better than previous ones because I stopped trying to manipulate the air flow and simply made the flow consistent. With consistent air flow the adjustment I need to make is with the juice feeder hole. It was a constant change the air and now have to change the feed and then back to changing the air. It was more trouble than it was worth.No more...again; just one adjustment as long as I have the two sealed up tight.
I'll make a few more to compare; especially with thicker ejuice. I have some 100% VG so it will be interesting to see how much different it is to the ratios I've run so far.
Hope this helps and best wishes if you decide to give it a go.
I saw a brief video from a guy..Sub Something; can't remember his name because he yanked the video about 10 minutes later. I'm not sure what he was shooing for, but the concept looked sound; just the execution wasn't there. Maybe that's why he pulled it; dunno. Anyway, I'm just a modder so I want to give him credit as soon as I get his screen name.