Well after lots of "testing" last night, I decided to see if I could reproduce my results from last night, or if I was just over medicated from test after test, so this is what I did and tried again this morning and I'm 10x even more happy with it.
My biggest issue was it seemed to be going through the tasty stuff too fast. Maybe this is just expectation after coming from a desktop v-tower and using an epen for smoking.
To me it seemed to be heating up too fast, either because of the can's not sitting tight enough to get a good seal at the top, the metal can's "feet" not allowing enough room at the bottom over the hole, using a can and screen in the two chambers and thus, not getting an even fit across the top, the way I was packing, etc. I came to the conclusion though that a good seal at the top is vital. if it's not sealed properly there by packing properly and using two of the same height chambers, the air you draw in that is heated just ends up all in the chamber, and not through the can/screen and just cooks whatever is in there too fast.
So I took two convection screens and put one in each chamber. Then I loaded another convection screen fairly tightly packed and put in it on top of the other screen. Now either this lifts the screen just enough off the bottom of the chamber so it's not sitting directly on it and creates a small tiny air gap at the bottom of the chamber to allow the air to come in better, OR, it push the screen that much tigher against the lid and helps force the air though the screen and material instead of around it. WOW. On 2, I got super tastys that lasted probably 15+ draws. Cranked up to 3, got some good clouds. No popcorn taste at all.
Next went to the oil can, put some concentrate in it. Put the can in the chamber, but with a screen in the chamber first. Started on 3. Again, either this forces a good seal at the top, or air gap at the bottom. WOW. Almost tasted like a hit of a nail. turned up to 4 half way through. Coughing and snot bubbles and clouds.
Next, dry herb in the oil can. Finely ground, tightly packed, and on top of a screen. Started on 3 being in a can. Taste that lasted for ever. It shut off on me twice due to the timer and I wasn't done the load. No popcorn taste. Turned up to 4. Finished it off, still no bad taste.
Next, nicotine e-juice. Soaked a pad with about 3 drops, put it in an oil can, again, with a screen already in there. Started on 1. Could taste the strawberry taste pretty good, but no clouds really. Turned up 2. got some nice vapors, but the taste was just a tiny, tiny, tiny bit too heated I think. I just use cheap epens but I know if I hold down my button too long, I get a too heated taste, quick button bursts and I can control the taste much better. With the e-juice, I think cutting a conduction screen and putting it on the bottom of the can, then the pad on top of that would just lift it up enough to get vaped by the heat and give good clouds on 2.
So my conclusion, a convection screen in each chamber is awesome. Then load on top of that. It also has the added benefit of keeping a screen over both of your holes so no material will ever get in either hole.
Why does this work ?
Could my vape chamber door be a tiny fraction too high, and I don't get a good seal and thus the air just heats everywhere in the chamber instead of through the material? I don't know.
could my vape chamber door be a tiny faction too tight, and it pushes the screen or can too far down and blocks the hole a bit and forcing the material to heat instead of air flow through it? I don't know.
Did I just come up with a better way for V4 or the can's to be designed? I don't know.
Does adding 2 screens in my cans and loading on top of those change my thinking from yesterdays "this is ok, I'll probably use it" to today's "wow, I haven't tasted anything so good from a vape ever"
When I get some more cans, I will experiment more. I think the oil can's are great, but I'd like to try drilling a few holes in the bottom, put a screen, then herb, block the 2nd hole on the silicon top so all the air flow is forced from the bottom hole, through the hole can and then into the mouthpiece. I would drill the holes near the back of the can since the draw is in the front, thus giving maximum heated air/convection exposure.
Anyone else wanna test my theories. lol.
Check it out... 
the mp is never a problem getting out as long as you have the tweezers it comes with. I let it heat up to level 3 then jack the mp out with the reverse end of the tweezers. Once its hot it comes out like butter. Those who are having taste issues need to stop putting weed in the cans. Imho, too much metal going on in there. Use the conduction screens for more air flow. My OG davinci has cans with silicone lids and filling those with weed yielded the same results but packing the chamber and using the cans as a tamper made the taste go way further.
, don't try this) the fragile part is the connecting wire running up the side.
