llAttachToAvatar and ownership

If I have an object try to attach to an avatar, it won’t work unless that avatar is the owner. Even if the avatar is the owner, this adds another unnecessary copy of the object to the avatar’s inventory every time. I thought I saw a note somewhere about how this could be prevented by setting the temporary bit in the object, but can’t get it to work.
I can give an object to an avatar, but it lands in their inventory not in-world. There is no way that I can see to change the ownership of an object so it can attach itself. (That does sound like a security issue). Here’s what I’m trying to do:
I have a dock that rezes sailboats. I want someone to be able to walk up, get in the boat and go. A few seconds later another one appears for the next avatar. The problem is that for various nefarious reasons, most of the sailboat is an attachment. It messes up the smooth operation of the system to make people acquire the attachment in a separate step. I’ve seen giant spaceships that are built partially as attachments, has anyone else found a way to deal with this? Is there something I’m missing?

Yeah, it's not easy. One way is to set the rezzed object for sale for L$0, then it can attach itself (after asking permission ) to its new owner.

needs to be set as for sale of the original, so make sure you're re-rezzing a new copy. what kind of boat is it that it goes over the limit of prims for it to be physical?

No, number of prims is not the nefarious reason that most of the boat is an attachment.