Yeah I used Nuki Nuts on my charmer, I think I had it on that image I posted with Lumia where it "just kept cumming" over and over, but if your production goes up high enough, you'll bounce back up to "barrel" and way bigger fast enough you need to play with that high pressure cumcannon between your legs one every couple of hours pretty quickly. Huge balls past a certain point just puts me in mind of really terrible infections and similar pretty much automatically, it's as nope for me as cervix penetration and womb-fucking is for women.
For the most part if I want someone with superhuman volume I just save edit the numbers after maxing what it could do in-game, bring it up to 10k or so for 4-5 hours for a cumflated character or companion to deflate again, this can be done pretty easily while still retaining "apple" sized or less (which is still kinda gross, but within the bounds of what Kas or a Minotaur tends to carry around). Usually what I'll do is that I'll go buy Vaush's potions and bring it up until it stops increasing volume and instead just increases testicle size (around 15 or so Virility Boosters usually), possibly also going to fuck the river Chimera a few dozen times if I don't care too much about Corruption (with Blessing those 15 boosters is only around 30 corruption, which can relatively easily be atoned if I care about it on the character, but 75 becomes problematic fast) then I complete Evergreen's quest so Meira comes home and have her max out the production via her menu, and use Incubus Cum to get Nuts Half Full and Messy Orgasm perks, at that point I feel I've done all I can legitimately do to increase things without getting into gross sizes, so at that point I export the save and edit it however much extra needed. If you don't want to cheat, then final Centaur Pack dick TF will also increase production past what the other sources will, as will Kas's Old Forest Valentine event, and finally you could get Corrupted Stud from several of Nash's super-expensive stock, which increases production and virility based on corruption, since at that point you're going to be basically DK anyway what with the other stuff.
Yes I do indeed have step-by-step plans to do the silliest things in this game taking way too much time and brain power than they are worth, from dick size to cum volume to gently gaping Ryn on my Horsecock. I blame my OCD.