Sir the 50 liter design is given by Focal itself for "deep and articulate bass". Also the F3 is 39.1hz not 41 hz.
Also what you are ignoring here is the "in car transfer function" (cabin gain in our case) which automatically increases the low end frequencies when the enclosure is put inside the car. The design discussed by you or the FR graphs being discussed are of open environments, where the "transfer function" of the cabin is not taken into account. The lower end will automatically be improved once the enclosure is put inside the car.
Now here is an example of the transfer function i mentioned. Look at 20hz, as per the enclosure graph its 72db at 20hz BUT the actual in-car level reaches up to 91db at 20hz that a 19 db GAIN..!! and the f3 you mentioned is only a 3db difference.
100 liters for a sub with the vas of 76 liters ???????
That would be more like putting the sub in a free-air or infinite baffle environment. Do you want to do that ?
We all know what happens to a sub which is designed for a sealed enclosure application, when put in an IB application, bye bye sub :P. Not to mention the poor power handling capability of the sub aswell..!!
20hz is inaudible and to most of our OLD EARS even frequencies much greater than 20hz is inaudible, then whats the point to tuning a sub to an extent which we cant hear?
Now lets talk about the Ported Enclosure:
33V2 as per the EBP values, this sub is NOT suitable for Ported Application. So lets just simply rule out the ported design altogether.
Now lets just assume we can make a 100 liters enclosure or a ported 22 hz enclosure. I see no point actually, specially in the integration part . If you disagree with me let me know, I got a few question about your designs which i will be more than glad to ask 
