Well they don't mix. That's what I learned today. I was using the catapult on the rat barricade quest, all alone, and I used the aim feature. The catapult aimed in my direction, and the front part actually went right over top of me. I was completely unable to move in any direction at all. With the rats bearing down on me and no DMs present I logged off (they weren't right in combat with me, more like a few rounds away). When I logged back in, I was out of the catapult. Still, this is dangerous!

How far does a halfling fly when used for catapult ammo?

50meters

More when you give them paper wings

And even more when you duck tape them into a ball

Useful info, thanks Ebok :D