Really hmmm my bad I guess I mixed that up ….? thought F1 was 1st cross was kinda unstable if those where from very first choice of bad parents to screw especially, like Old Bobylynn and her cousin Billy to bang in the back woods and they give you some inbred looking harder to find F1s that have to be worked into a decent cross by choosing your best phenos out of alot more beans. But you put 2 or even 3 sexy adults together very compatible to bang and they give you good F1s with your Hybrid vigor.
F1 is the first cross, but it has to be the first cross of two plants with completely different genotypes. In terms of stability, f1 is actually much more stable than f2, since you see a lot more recessive genetics pop up in the f2 generation. For instance, lets say purple is a recessive gene and let's call it p (p for purple, lower case since it's recessive), and lets say green is a dominant gene and let's call it G (For green, capital for dominant). Now we breed A purple plant with genes pp to a green plant with genes GG. Every single member of the F1 generation will be Gp, and will express green, with no purples to be found. Now we cross two of those, Gp x Gp, and our F2 generation will be 25% GG, 25% pp, and 50% Gp, giving us an F2 generation that will be 25% purple 75% Green (66% of which will carry the recessive allele for purple). If you were trying to get purple you could keep isolating and breeding. Since most of the TGA strains share parental lineage, crossing them won't yield an F1, but rather just backcrossing or moving forward another filial generation. Because Hybrid Vigour as a natural phenomenon is correlated most strongly to the dissimilarities in the genetics of the crossing plants, crossing two plants that share genetic lineage is unlikely to induce true hybrid vigour, or heterosis.
"The physiological vigor of an organism as manifested in its rapidity of growth, its height and general robustness, is positively correlated with the degree of dissimilarity in the gametes by whose union the organism was formed … The more numerous the differences between the uniting gametes — at least within certain limits — the greater on the whole is the amount of stimulation …"
So yeah, inbred Bobylynn screwing her cousin Billy wouldn't give you F1 hybrid vigour because they are cousins so they share too many genetics.