As a design challenge, I don't think it presents much of a problem. I mean the bugs, yea, but if everything is sprouting, or dangling, from the same origin point, it shouldn't be too hard.
I dunno how Fek has chosen to model that part of the anatomy in depth, but for the testicles, if it were a bag shrink-wrapped over two spheres, then adding spheres is nothing. Cocks, basically the same thing, but with whatever cock model ya got. If they have a sheath, just have all cocks sprout from the same sheath, the sheath just stretches wider. 
Interacting with these things is its own challenge, but really I think Fek has been looking for a way to just build a logic system around these model interactions to avoid clipping between models (i.e. if you're fucking a cock, you don't clip through another cock in a weird way, etc.). Ball play is just the same. 
I dunno, does that make sense? Am I talking out of my ass here?

On the other hand though, I might fucking freak out if I walked around, looked in a mirror, and then saw my fursona.

You do you. I support you.
Also you should take this up at the cock growth posts out there.

Thanks because my Infestation tab ain't doin' so hot. I can understand I guess... Though I'm glad this is in the like top 20.

Do you think this guy thinks we're actually talking about a real lab?

Of all the places... leave us to discuss porn in private, you creep.

Ok so this is just a genuine question, last time I ask, sorry if I'm wasting anybody's time...

What is this fetish called? I feel like it's similar, right? I mean they kinda blend, honestly. I just like the swirling around and wrapping around the testicles part inside the ballsack. And honestly a lot of oviposition porn has them injecting directly in to the testis or eating and replacing the testis.

I'd say it's infestation, but bugs and worms and stuff I think are another story...

Again I'm sorry if I'm breaking some kind of hard porn rule, or if this grosses anyone out.

Credit to Dmitrys and Wyntersun

• Sorry if I'm breaking some kind of rule on hard porn... but this. This is what I'm talking about.
• Credit to Dmitrys and Wyntersun

I dunno if y'all who voted for this are in to this kinda thing but some of ya must be.

You know what the name is of the fetish where tentacles distend through the urethra and then distend the ballsack as they wrap around the testis? Like this?

(Sorry if I'm breaking some porn rule.)

<credit to Wyntersun>

Hey we never went in to the whole like... infestation idea, right? That's not a suggestion. I don't know if people really consider that hard guro... you know what I mean though, right?

I wanna see whatever tentacles distend through the urethra and then distend the ballsack as they wrap around the testicles, or eat them or whatever...

I dunno what that's called, exactly. I think it's infestation...