It seems to me that while there are limits for each person, those limits will be a soft cap in nature rather than a hard defined limit. That boundary will be different for each individual, and I don’t think there is any way to test or determine those limits beyond trial and error.
If I’m not mistaken, gains basically come from three sources. 1) Improved EQ. 2) Stretched/elongated ligaments. 3) Micro-tears in the tunica, which prompts the body to repair it by adding collagen to fill in the tears. More tissue means more size.
There’s a hard limit to category 1. Once you reach 100% effective EQ, there’s nothing further to be gained from it. The importance of EQ will increase as you make category 3 gains, though. It is possible that a circulatory system that gives you high EQ with a smaller unit may not be up to the task of a larger unit, and may require vascular exercises or supplements to maximize and keep up.
There is some degree of limit for category 2. The ligaments can probably stretch beyond what would be useful, since stretched ligaments are only helpful to allow more buried shaft to present. Once you run out of buried shaft, extra ligament length does nothing positive. In theory you may be able to gain more here as well, as your category 3 gains progress.
Lastly, your tunica gains most likely do not have a hard cap, but rather a soft cap of sharply diminishing returns. There may not be any way to accurately determine it that however. Like with other collagen-based tissues, injuries to the tunica should repair through the deposit of additional collagen. If I’m not mistaken however, injuries to tendons and ligaments tend to be less flexible than the original tissue. It seems to me then that the more you gain through the deposit of new collagen, the less elastic you will be and the more difficult it will be to gain further. That is all an assumption but one that seems logical to me. Another interesting feature of collagen-based tissues is that the more tension the tissues are put under, the more the collagen fibers align and strengthen. This is probably what explains the phenomenon of conditioning and the need for deconditioning.
If I’ve made any faulty assumptions or my reasoning is flawed please point it out. I’m still here learning as well.
Lastly there is no way that I am aware of to increase the spongy tissue of the corpus cavernosum. I suspect that its ability to expand is indefinite enough that only in the most extreme cases would you end up stretching the tunica beyond the cavernosa’s ability to fill it though.
Starting Stats Jan 2019 - BPEL: 6.75", MSEG: 5.875"
Now - BPEL: 7.0625", MSEG: 6.25"