Auto-unsitting?

I recently figured that incorporating a chair into a device of mine, and taking the user's controls would be more prim efficient than the current system (Touch buttons). The system was working, I got to the point where all the prims were linked up correctly again, and I was sitting right. Then I got unsat.
At first I though I might've hit the "Stand Up" button. But as it turns out, it seems that the llSetPrimitiveParams unsits the user automatically..? I've muddled with !Meta's Elemental vehicle, and it changes FAR more than my prims do (Mine is a simple texture change, nothing more), yet you can sit in it and not get thrown out when it transforms. Am I missing something? A "Don't throw people out of the seat" option somewhere?

Did you try defining a sit target? that may fix the issue.

I have the sit target, thus the point of the chair.

Some prim params set will cause any sitting avatar(s) to stand up. PRIM_TYPE being the most notable. Have not heard of a situation where PRIM_TEXTURE causes that, though. Have you tried llSetTexture() instead?

You might try using a tiny invisible linked prim with the Sit Target in it instead, too.

I thought about that, but the problem lies in the fact that the only way to resize or reposition the texture is in llSetPrimitiveParams(). Since the two screens on the machine rely solely on moving and resizing textures, I have no choice but to use it.