Hm... Princess is a hung almost-horse-cocked dickgirl, gianna is a futa with detachable huge horse cock, millie is a cowgirl, and zephyr is futa cowgirl. Yes, they are not huge-dicked furry futas, you are all right.
You need seduce him/her enough times. It would appear in main companion menu as "Sex", but he/she would decline it at first so you'll have to talk about disciplines and confront.
You can't get perk itself. Masturbation scene requires being cat-morph (and detected as one) now, not being taur and having cock not over 12" long (it breaks the scene). I think I'll change requirements from race to legs/tail/ears to be simple.
Vala is actually the only way. The chance to grow is diminishing when you are above 9 ft, so this would take some time. And groving more would break space-time continuum in many scenes, worse than tauric body does.
1) Download.
2) Open in browser/flash player.
You can type it anywhere. I prefer codex screen.
Forgot to handle it in GroPlus/Reducto/OviElix/Dyes. Will fix.
It is actually strange, when on initial encounters in swamp he is quite freindly to female characters, but once he got to Tel'Adre he suddenly goes cold.