Hello, also BigBuilder Dual Feed Original user, you had a very good initiative
The printer is very good, but of course, needs training…
Its print size is attractive and can be disappointing when at the half of the print something goes wrong. As it’s very versatile it’s not exactly the most “ready to print out of the box” printer you can find !
It happened to me several times… but never gave up, that’s how I learned to match print speed / heat depending on filament brand, and expected result.
So, I will try to answer and/or share with you my experience and advices based on your topics :
1) extruders grip is way below the quality I would have expected, I need to screw the tensionner to the max to ensure a constant grip.
No, don’t do that, you will break your filament, and you don’t want that ! 
Try increasing heat for 5 or 10°C (unless you’re already at 220°C, which way too much by the way for PLA)
Check also if your extruder is clean, as the path between extruder and motor.
You can use Prepare / Move Axis / 1 mm / Rear (or Front) with extruder unscrewed to check if the grip pressure is enough
If you put too much pressure, again, you will kill your filament after two or three back and forth movements
2) Shake-it, baby, but not too much! I had to reinforce it with linking top sides to the wall with aluminium bars, otherwise, the shaking lowers the quality a lot! And the (hot) bed is shaking in the oposite direction, which was making it worse.
Good Idea, if you can share some pictures of the result, it would be great !
I’m working on my spare time on printable accessories to mount on the printer, so anyone can fix the printer to something heavier
3) Seems flex is not an option, again the grip is insuficient. But here if I insist and screw to the max, then the problem is no more the grip, but the filament jamming between the wheel and the hot end entrance
Same with solvable filament, and I found the good pressure, but again, after 1 or 2 hours, it goes in the side fan, because filament got burnt.
because it would be better to set different temperatures for each filament. So each time the extruder goes to the wipe tower, the nozzle increases or decreases heat, but it seems nozzles don’t really like it…
4) Bed leveling: thats an hard one. The 4 plots are only resting on top of the 4 screws, and it is very difficult to have it even WITH the 4 screws forming a perfect flat square.
Solution : add some skirt, and adjust the bed level in direct.
I used to adjust with a 0,3 mm thick paper to be precise… wasting my time !
Way faster with some skirt !
But yes, it’s a missing feature, definitely !
5) Support: I got it second hand. was barely used for two or 3 big prints. I had a hard time to get the code for their (very, if not amazingly) basic color mixer. And they would not even give me any advice. Allright. I then bought the accessories pack, and I also ordered two new wheels and 6 packs of filament and a new 0.8 head. They forgot the wheels and the head in the package. Since the beggining, I have the feeling either they don’t care, or, worse, they hate me for buying it second hand. So what, it was resting there and we have only one planet, right? Anyway, I gave them the serial number as asked, and obviously they wont reply to that neither. Sic. S, if YOU guys could help…
help about client support or color mix serial ?
Color mix serial will be tough because we have only one…
By the time I bought mine actually, it was already very difficult to get support. Plus the reseller was frightened because he apparently had a lot of returns so he didn’t even want to check the printer. (totally illegal, if you refer to european consumers protection plan)
It’s interesting, because in other professional domains, when you buy a 3000 € machine, you can at least get some help !
But apparently, it seems we are just rich enthusiasts, who have enough money : It’s very bad, I totally agree with you on that point
Again about Color mix software, when I bought my printer it was 50 € more to get a license, and the flex kit (which I suspect to be total marketing bullshit) was also a paid option. A bought the kit but I asked to get my licence for free. Now it’s included, Great !
I mean, great for new customers, but I won’t congratulate them for the zero efforts they made to their loyal early customers
6) Underscaled fan & duct. I installed a huge radial fan on top of the printer, that got better, but if anybody have the perfect solution duct (redesigned?), I’m interested.
Could you show some comparison pictures for prints impacts ?
7) Example of config for dual color printing in simplify 3D? I have done a lot of color mixed tests but was not able so far to find a working config for dual colors printing with prime tower?
I work with the old Cura (15) wich is adapted with this printer.
And I’m too lazy to reconfigure a new machine in a new software 
8) No, I’m not in love with that printer at all so far.
Sad, because it’s not responsible for its resellers and producers. It’s still a very good piece, very versatile
Of course, you will have A LOT of trying and fails… but you have all these settings you can adjust in direct, and finally you get better prints than other machines. Not every time, but most of the times, and since I bought it never died, the electronics are reliable (compared to a Makerbot, I don’t regret my investment)
9) Could you help me change that? :-)))
You had a great initiative, and I thank you for that.
I think we are alone, and 3D Builder won’t help us. They told me several times “Each filament needs its specific settings, It’s up to you to find the good ones. Good Bye”
That’s it
We could start a shared document to refer which works best based on five aspects :
filament brand / filament type / print speed / nozzle heat / layer height
maybe a sixth one : same filament brand, but different color… I noticed it could affect print quality
Plus with or without heated bed (which I don’t have personally)
Best regards
