Sitting on the ground - how to enable?

Greetings,

When designing a surface indended for sitting, is there a way to conifgure the surface so that an avatar who sits on it will use their "sit on the ground" animation rather than their regular sitting animation?

You have to place a script in the surface that stops the standard Sit animation (plus any other Sit animation that their AO might have started), then starts the Sit animation you want to use.

There's a script here you could use: /15/83/112151/1.html - although that was originally designed for poseballs, not surfaces, so you may need to adjust the sit target a bit.

Along the same lines, I think, why do nearly all "sit on ground" animations make my AV sink into the ground? Someone told me it's because I'm shorter than average. Is there a way to adjust the animations so that they seat me correctly?

Unfortunately not. In animation, your avatar's "base" is their hips, and this is the only part of your body whose actual location in the world is tracked. Everything else - arms, legs, etc - are located only based on their relative angle and direction compared to the hips. All of the values used in animations have to be set to absolute values when they're uploaded, so apart from designing generic animations, there's no way of compensating for height. This can create all kinds of problems - for example, if an avatar with short arms and legs used a "crawl" animation, they can easily wind up floating above the floor.

Ahh, that explains why in any couples dance, I float about a foot off the floor!

I have a surfboard that does that too... my feet are a good 2-3 feet off the surface, so it looks completely ridiculous.

Unfortunately the seller made it no-mod, so I can't even go in and adjust it myself.