Ok, so, apart from the fact that FORCEBALLS DO NOT WORK, I tried FB cancels a bit.
So I tried the following strings with the following combo: f344 -> FBC -> <string> -> glassesKB -> f344 amp camera -> j2 b2 f3 121 shadow kick.
For the <string> part we have:
a) 12 - damage : 457.93
The best string to use, ever, especially online. Since we don't have an f1, it will always come out straight out of the dash cancel and the frame window is EXTREMELY generous you can even do it in 150 ping.
b) 233 - damage : 456.37
This string suffers from the same problem as 34, as you need to dash clean and not hold forward as you do the string(otherwise you will get f2 and fail). However, because of the fast startup of 2, it's a lot more easier than 34. However, the damage scaling is worse than 12, and it's harder to do, so literally no reason to do this ever
c) f344 - damage: 472.66
This string, although f3 is a lot more slower than 3, will come out straight out of the dash cancel and it actually feels easier to do than 34. The damage is nice to, so I would most surely choose this approach offline.
d) 34 - damage: 497.84
The best one although the hardest one to pull off, it gives you the biggest damage but you need to actually grind your ass off to do it, and online in >100 ping I wish you the best of luck. You need to clean dash cancel with exact 2 forwards and lift your finger off the direction as you do 34 (otherwise you will get f3 and lose). It feels horrible imo and I would only go for this if you have a shitload of time to practice at home to become a pro.
In conclusion, if you're not extremely elitist, f344 is the way to go offline as you only lose 2.5% damage.
However, if you really want to just do the combo and do not care about timing and online, I suggest just doing 12. It is a 4% damage difference indeed, but if you have to choose between losing 4% or dropping the combo and getting teabagged, I would suggest you choose losing 4%.
Happy canceling.