A part of me regrets this already... >~<

What size of belly is your fav size?

Hmm...This is actually a bit hard to answer due to some variables. Artist, Perspective, Pose and the shape of the belly (usually determined by method: preg, infl, etc).
...I like a bunch of sizes...
I guess the most ideal size for me would be somewhere past the point of a 9 month pregnancy...but not really big to the point where the belly would touch the ground when standing. (while sitting is fine tho~ <3)
Ok visual guide: (Roxanne for the 1st) 1 2 3 4 Anywhere around these lines are great!

I'm curious to know what yours is. Care to share?

Yeah. Mine would be around these sizes:
http://www.furaffinity.net/view/15922586/
http://www.furaffinity.net/view/17362243/
http://www.furaffinity.net/view/14965439/ (the gal on the far right)
http://www.furaffinity.net/view/14208321/ (Again, gal on right)
http://www.furaffinity.net/view/11886810/
http://www.furaffinity.net/view/11751367/ (is about my max size)

Basically anything where the bottom of the belly is between the knees and ankles.
Next questions:
What is fav filling of said bellies? Water? Air? Pregs? Cum? Eggs (visible or non visible bulges?)
How soft or firm do you like your bellies?

That's a nice size.
Favorite filling? It's almost a tie between water and cum...but cum wins*. heheh >w<
*only valid when tentacles are involved

Hmm that varies by size and method. If around my ideal size, it's a mix of soft and firm.
Like firm enough to retain it's overall shape, but soft enough that your hands could press into it a bit~

Me I like around pregnancy firm, but that is just me.
Another question: Do you RP?

Not often, but I do. Usually if I am asked, "Do you want to RP?" I will say no.
The secret to getting me to RP, is to just do it. I like it when it's spontaneous. ^^

LOL I see!
If you had a gal from any picture come to life, which one would you choose?

Nefertiti the star dragoness so I could rule the world
Probably Roxanne. Many things I like about her~ >u<

"Nefertiti the star dragoness so I could rule the world"
*cue evil laugh*

Just so you know, while I was on my quest for the perfect belly, I found my gallery was lacking that type.
I'm going to fix that now~ <3

*grins* Awesome!