Well, that depends on the nature of the gain. Girth, if it is due to alot of swelling or fluid build-up instead of tunica stretch tends to fade. If the additional legnth is partially a function of the soft tissue glans/CS and PC exercises are neglected, perhaps a slight decrease will occur. I am a minimal gainer in L and I have not noticed much if any decrease, but my gain is shy of an inch. Larger gainers may comment differently. I don’t neccesarily think that it is a question of manual versus hanging per se, but do remember alot of manual techniques do make significant use of the PC muscles.