Help with bench seating/ adding bones

I have been wanting to do something similar but with like two or three chairs on one side and then a bench on the other side. I bet it is possible.

I remember when I had to deal with the mouse/hand issue for the computer conversion from TS3 to TS4 I was told to use milkshape. I was given a little tut on it and was able to fix the problem. I am wondering if you need to get your bench lined up exactly with the bench on the picnic table and get the bones "transferred" over to the new bench. You may not be able to move your slots without the slots being moved on the bench of picnic table.
Also, if there are four bones for seating on the EA mesh, then there are four bones for seating on yours. You would have to add another bone to both meshes or to just yours...in blender?
the sgl bed i made had to have the same binding and bones as the EA. and that was done in blender. have you tried that yet? and how big are the slots on the EA picnic table bench?

when I added the bones to the computer, it was in blender...then when i fixed the mouse/mousepad it was in milkshape. I didn't do anything in the warehouse as far as the bones go. because I used TSRW I had to make the laptop compatible with s4s again....that was when I went into the warehouse. There is a tut that inabadromance directed me to when it came to bones and weights. let me see here...(it deals with a CAS earring, but OM did the tut and she explains some things) link
also, if that doesnt help, there is a site at facebook called sims creators community cc and tech. You can ask your question there and they can help you. here is the link
there is another tut i found that om did...it is making a candle have three flames...it is object tuning that might help as well. here is the tut
I am wondering if the footprint has to be adjusted as well because when you have a table that sits three on each side the sim has to move the chair in the middle just like they do with the edge chairs. it is easier for the sim to sit on the edge of the bench because they turn and move. but in the middle.... i am thinking it would be a bit more difficult. When looking at the a regular park bench...the sim will sit in the middle, but easily because they just turn around and sit, but the middle of the bench is blocked by the table. so the animation on the sides of the bench would have to be tweaked to get the sim to sit in the middle of the bench. 
I wonder if necrodog would be able to help with this one. He is really really good with animations and tuning. I wish OM and/or Andrew would respond to this. g1g2 is good with stuff like this as well....may be SACRIFICIAL aka sacrificial could help too.
I am stumped just like you are and am very curious to see how this works out. I have been fiddling around with the blend file and nothing. there has got to be a way to do this. I am so sorry I am ignorant, but sometimes two heads can be better than one and thinking out loud about certain things can spark something and you think....o yeah! that would work. This is going to be tough, but in the end...I know it will work. So many people said that the laptop wouldn't be able to work, but it did!