After a bunch of searching, I came across this...
Most notable excerpt is as follows, "
In this study, amounts as small as 15 mg and as much as 120 mg of topically applied testosterone gel were required to reach physiologic levels of testosterone, dihydrotestosterone, and estradiol, which implies an absorption efficiency of anywhere from 50% to as low as 6%. This finding is consistent with other researchers using gels,[28,33]
where great interpatient and intrapatient variability has been observed. Patches, such as the Alza Testoderm TTS, which, in fact, actually contains 328 mg of testosterone, also suffer from low absorption efficiency.
The scrotal patch contains only 10 mg of testosterone.
Androderm 5 mg patches contain 24.3 mg of testosterone.
Thus, there exists little qualitative difference in the efficiency between gels and patches. Alza researchers originally developed their first patch, Testoderm, to be applied to the shaved scrotum. They found that, compared with other skin sites, the scrotal skin is about five times more efficient at absorbing percutaneously applied steroids.[17,24]"
According to the article, natural production is about 7-10mg/day, and the products tested seemed to try to introduce 5mg into circulation. So this seems like a lost cause unless you want to cake gel around your scrotum and wrap it in saran wrap to prevent it from drying out in an attempt to get 50% absorption, or use it as some sort of gel suppository...