Although you have already passed your growth seasons, you can still balloon your penis. The penis is a blood balloon which can be inflated by the parasympathetic nervous function (acetylcholine action) with the presense of the erection mediator NO (Nitric Oxide) agents. When bioenergy is stored in the parasympthetic sexual nerve, the bioelectric action voltage will actuate the penile erection.
Since your body can still synthesize L-Arginine, the NO agent and the human Growth Hormone releaser,
all you need is the parasympathetic nervous action potential. To achieve this, you need a testosterone burst and burning to charge the parasympathetic sexual nerve. The gentle-action, therapeutic supplement is ViaGrowth-I/Fibra (item 1-002) puls Ginseng Power Max 4X (item 2-007). The instantaneous action formula is ViaGrowth-III/Fibra (item 1-004) puls Ginseng Power Max 4X (item 2-007)
https://actionlove.com/cgibin/herbform.htm
You also have to learn how to hold ejaculation back several times to balloon the penis. Remember that your penis becomes maximum when you are about to come.
If you can produce serval maximums in a love session or stimulation, your penis can reach 140%, that is, about 6.3 inches. The Penile Ballooning Method is given in
https://actionlove.com/cases/case7648.htm
To learn how to hold back ejaculation, you have to learn the anal breathing method that help you switch your nervous function from sympathetic to parasympathetic during sex or sexual stimulation, and channel excessive sexual energy from the prostate back to the brain via the spinal cord (water pathway ) and the Governing Vessel (the Fire Pathway) of the acupuncture network.
http://www.actionlove.com/tao/image/anal.jpg